(1 point) Determine whether the following matrices are in echelon form, reduced echelon form or not in echelon form. 8 1 1 0 a. Choose 1 5 0 0 0 7 0 9 1 1 b. Choose -5 7 1 0 0 1 0 C. Choose 0 1 0 0 -10 -6 -] 1 1 0 1 d. Choose 0 1 1 0 0 -3