Choose the right answer out of a, b, or c for each problem. The vectors a, b, and c span R^3. Vectors a, b, and c do not span R^3, but they span vector d. Vectors a, b, and c span a 2-dimensional subspace R^3. a, b, and c are vectors. Then the expression a x c + b x a is Meaningless. A vector collinear with a. A vector orthogonal to a. Vectors a and b are some vectors in a space with inner Euclidean product, and it is known that ||a + b|| = ||a - b||. Then it follows that b = 0. a and b are proportional to each other. a and b are orthogonal. If A and B are square matrices of the same size and each of them is invertible, then Matrix BA is invertible. AC = BC for any matrix C of the same size as A and B. None of the above is true.