What conditions on a matrix $A$ insures that $A{\bf x}={\bf b}$ has a solution for all ${\bf b}$ in ${\mathbb R}^n$?

Select the best statement. (The best condition should work with any positive integer $n$.)

A. The equation will have a solution for all ${\bf b}$ in ${\mathbb R}^n$ as long as no column of $A$ is a scalar multiple of another column.
B. The equation will have a solution for all ${\bf b}$ in ${\mathbb R}^n$ as long as the columns of $A$ do not include the zero column.
C. The equation will have a solution for all ${\bf b}$ in ${\mathbb R}^n$ as long as the columns of $A$ span ${\mathbb R}^n$.
D. There is no easy test to determine if the equation will have a solution for all ${\bf b}$ in ${\mathbb R}^n$.
E. none of the above