Answer
a) Both $p$ and $q$ have the same sign (both are either positive or negative).
b) $p$ and $q$ have opposite signs.
Work Step by Step
a) If both $p$ and $q$ are negative, then $c$ is positive. If both $p$ and $q$ are positive, then $c$ is positive.
b) For $c$ to be negative, either $p$ or $q$ must be negative. However, both $p$ and $q$ cannot be positive or negative. (Otherwise, $c$ is positive.)
