<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>0009 - Disclosure - 3. INVENTORIES</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>From2012-12-01to2013-05-31</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0001436549</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2012-12-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-05-31T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="6 Months Ended" /><Label Key="Calendar" Id="1" Label="May 31, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>us-gaap_InventoryDisclosureAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Inventory Disclosure [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_InventoryDisclosureTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="From2012-12-01to2013-05-31" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 45pt"&gt;Inventories consisted of the following:&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

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        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;As at&lt;/b&gt;&lt;/p&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;November 30,&lt;/b&gt;&lt;/p&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;2012&lt;/b&gt;&lt;/p&gt;&lt;/td&gt;
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        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;As at&lt;/b&gt;&lt;/p&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;May 31,&lt;/b&gt;&lt;/p&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;2013&lt;/b&gt;&lt;/p&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: #CCEEFF"&gt;
    &lt;td style="width: 78%; text-indent: 0pt; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Raw materials&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
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    &lt;td style="width: 1%; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 9%; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;&amp;#160;624,444&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
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    &lt;td style="text-indent: 0pt; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Finished goods&lt;/font&gt;&lt;/td&gt;
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    &lt;td style="text-indent: 0pt; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Equipment (i)&lt;/font&gt;&lt;/td&gt;
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    &lt;td style="border-bottom: black 1pt solid; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;126,966&lt;/font&gt;&lt;/td&gt;
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    &lt;td style="border-bottom: black 2.25pt double; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;1,196,798&lt;/font&gt;&lt;/td&gt;
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    &lt;td style="border-bottom: black 2.25pt double; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
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&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in"&gt;&amp;#160;&lt;/p&gt;

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    &lt;td style="width: 96%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;During fiscal 2012, certain oil processing research and development related equipment previously sold in fiscal 2011 was returned.&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
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&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for inventory. This may include, but is not limited to, the basis of stating inventory, the method of determining inventory cost, the major classes of inventory, and the nature of the cost elements included in inventory. If inventory is stated above cost, accrued net losses on firm purchase commitments for inventory and losses resulting from valuing inventory at the lower-of-cost-or-market may also be included. For LIFO inventory, may disclose the amount and basis for determining the excess of replacement or current cost over stated LIFO value and the effects of a LIFO quantities liquidation that impacts net income.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 210

 -SubTopic 10

 -Section 50

 -Paragraph 1

 -URI http://asc.fasb.org/extlink&amp;oid=6361739&amp;loc=d3e7789-107766



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 -Name Accounting Standards Codification

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 -Publisher SEC

 -Name Regulation S-X (SX)

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