Which of the following subsets of R3×3R3×3 are subspaces of R3×3R3×3? A. The 3×33×3 matrices of rank 11 B. The 3×33×3 matrices with all zeros in the second row C. The 3×33×3 matrices with determinant 00 D. The 3×33×3 matrices with trace 00 (the trace of a matrix is the sum of its diagonal entries) E. The diagonal 3×33×3 matrices F. The 3×33×3 matrices whose entries are all greater than or equal to 00