$(\mathbb{Q},+) $ and $(\mathbb{Q} \times \mathbb{Q},+)$ are not isomorphic as groups I need help in solving this assignment question in abstract algebra.

Prove that $(\mathbb{Q},+) $ and $(\mathbb{Q} \times\mathbb{Q},+)$ are not isomorphic as groups .

I am unable to find a property that one of group would satisfy but not other despite thinking a lot .
Kindly help.
Thanks!!

In $(\mathbb Q,+)$, every finitely-generated subgroup is cyclic. In $(\mathbb Q\times\mathbb Q,+)$, the subgroup $(\mathbb Z\times\mathbb Z, +)$ is finitely generated but not cyclic - it is of rank $2$.
