What conditions on a matrix A ensure that Ax=b has a solution for all b in Rn? Select the best statement. (The best condition should work with any positive integer n.) A. The equation will have a solution for all b in Rn as long as the columns of A span Rn. B. The equation will have a solution for all b in Rn as long as the columns of A do not include the zero column. C. The equation will have a solution for all b in Rn as long as no column of A is a scalar multiple of another column. D. There is no easy test to determine if the equation will have a solution for all b in Rn. E. none of the above