Question

What are the expressions of vectors ab~, cd~ and be~ in terms of a and b?
A. ab~= -a+b, cd~= -b+a, be~= 2a-b
B. ab~= a+b, cd~= b-a, be~= 2a+b
C. ab~= -a-b, cd~= -b-a, be~= 2a-b
D. ab~= a-b, cd~= b+a, be~= 2a+b