Suppose A is a 4x3 matrix and B is a vector in R⁴ with the property that Ax = B has a unique solution. What can you say about the reduced echelon form of A? Justify your answer.
A) It must have at least one row of zeros.
B) It must have at least one column of zeros.
C) It must be a square matrix.
D) It must be a row-reduced echelon form.
E) It must be a column-reduced echelon form.