Let f : Z → Z2 be a homomorphism of groups defined by
\(\rm f(a)=\left\{\begin{matrix}0,&if \ a\ is \ even\\\ 1,&if\ a\ is\ odd\end{matrix}\right.\)
then Kerf is :
1
The set of all odd integers
2
The set of all even integers
3
The set of all natural numbers
4
The set of all real numbers