Provide an Appropriate Response $A$ Is An $m \times n$ Matrix And $B$

Provide an appropriate response.
-Suppose that $A$ is an $m \times n$ matrix and $B$ is a $p \times q$ matrix. Under what conditions will the sum $A +$ B exist?

A) If $n = p$
B) If $\mathrm { m } = \mathrm { p }$ and $\mathrm { n } = \mathrm { q }$
C) It is not possible for the sum to exist.
D) The sum will always exist.