Let $T$ be a linear transformation from ${\mathbb R}^r$ to ${\mathbb R}^s$ .

Determine whether or not $T$ is onto in each of the following situations:

 1. $r=s$
 2. $r<s$
 3. $r>s$

A. T is onto.
B. T is not onto.
C. There is not enough information to tell