Which of the following is NOT a subspace of the vector space V of 2×2 matrices?
Options:
A) The set of all symmetric 2×2 matrices.
B) The set of all skew-symmetric 2×2 matrices.
C) The set of all 2×2 matrices whose entries add up to 0.
D) The set of all 2×2 matrices whose determinant is an integer.