Let `alpha in RR` and the three vectors `vec(a) = alpha hati +hatj +3 hatk, vec(b) = 2hati +hatj - alpha hatk` and `vec(c) = alpha hati - 2 hatj +3 hatk`. Then the set S = {`alpha : vec(a), vec(b)` and `vec(c)` are coplanar}

Options

A. is singleton
B. is empty
C. contains exactly two positive numbers
D. contains exactly two numbers only one of which is positive

Answer

B