&lt;p&gt;DIFFERENCE BETWEEN &quot;MUST&quot;&amp;nbsp; ; &quot;MAY&quot; and &quot;CAN'T&quot;&lt;/p&gt;&lt;p&gt;&quot;MUST&quot;&amp;nbsp; INDICATE CERTAINTY&lt;/p&gt;&lt;p&gt;&quot;MAY&quot; INDICATE DOUBT OR UNCERTAINTY&lt;/p&gt;&lt;p&gt;&quot;CAN'T&quot; INDICATE IMPOSSIBILITY&lt;/p&gt;&lt;p&gt;EXERCISE OF APPLICATION IN PAGE 47 IN S.BOOK.&lt;/p&gt;&lt;p&gt;&lt;br&gt;&lt;/p&gt;