Item 2.
Assume that \(a\) or \(b\) is even - say it is \(a\) (the case where \(b\) is even will be identical). That is, \(a=2k\) for some integer \(k\text{.}\) Then
\begin{align*}
ab \amp =(2k)b\\
\amp =2(kb)\text{.}
\end{align*}
Thus \(ab\) is even.