Hello Math experts, i need some help

let $\displaystyle X$ be a topological space.

Let $\displaystyle A \subset X$ and let $\displaystyle r: X \rightarrow A $ be a retraction.

Given $\displaystyle a_0 \in A$ , show that

$\displaystyle r*: \Pi_1(X,a_0) \rightarrow \Pi_1(A,a_0)$ is surjective

thanks