When q is 0, B=0, and A=0 is not true. The textbook says that the zero vector is parallel to any non-zero vector, but it does not stipulate that two zero vectors are also parallel.

For b:

If Q 1 and Q2 are both 0, then Q 1*A+Q2*B=0, and A and B can be arbitrary vectors (not zero), so A and B are not necessarily parallel.