Easy# Infinitely Many Integral Solutions

NUMTH-$8F6@E

Let $a, b, c \in \mathbb{Z}$. Then, the equation $ax + by = c$ has infinitely many integral solutions if $\gcd(a, b) | c$ and no solutions if $\gcd(a, b) \nmid c$.

Which of the following equations have infinitely many integral solutions? Select **ALL** that apply.