Maurice Receives $100 as a Birthday Gift

Maurice receives $100 as a birthday gift.In deciding how to spend the money,he narrows his options down to four choices: Option A,Option B,Option C,and Option D.Each option costs $100.Finally he decides on Option B.The opportunity cost of this decision is

A) the value to Maurice of the option he would have chosen had Option B not been available.
B) the value to Maurice of Options A, C and D combined.
C) $100.
D) $300.