Find the null space for $A = \left[\begin{matrix} 2 & 1 \cr -5 & 4 \cr 7 & 1\cr \end{matrix}\right].$

What is null$(A)$?

A. ${\mathbb R}^3$
B. span$\left\{\left[\begin{matrix} -1 \cr 2 \cr \end{matrix}\right]\right\}$
C. span$\left\{\left[\begin{matrix} 0 \cr 0 \cr 0 \cr \end{matrix}\right]\right\}$
D. span$\left\{\left[\begin{matrix} 2 \cr 1 \cr \end{matrix}\right]\right\}$
E. span$\left\{\left[\begin{matrix} 1 \cr 2 \cr \end{matrix}\right]\right\}$
F. $\left\{\left[\begin{matrix} 0 \cr 0 \cr \end{matrix}\right]\right\}$
G. ${\mathbb R}^2$
H. span$\left\{\left[\begin{matrix} 2 \cr -5 \cr 7 \cr \end{matrix}\right]\right\}$
I. none of the above
.