Is W is a subspace of V? If not, state why. Assume that V has the standard operations. (Select all that apply.)
W = {(x1, x2, x3, 0): x1, x2, and x3 are real numbers}
V = R4

A) W is a subspace of V.

B) W is not a subspace of V because it is not closed under addition.

C) W is not a subspace of V because it is not closed under scalar multiplication.