If n is even, which of the following cannot be odd?
I	n + 3
II	3n
III	n^2 - 1 Choose one:
A) I only
B) II only
C) III only
D) I and II only
E) I, II and III
Let take a look at I   n + 3   we have this formula : even + odd = odd   =&gt; n + 3 is odd   III: n^2 - 1   n^2 always be even   so n^2 - 1 is odd   =&gt; only II is always even   =&gt; answer is II only
<result>B</result>
If n is even, which of the following cannot be odd?
I	n + 3
II	3n
III	n^2 - 1