It is B.
First you have to add -2.4 by itself until you get to 12(that is 5 times.) Then, you divide -2.4 by 2 and get -1.2. Next, add them! -12+-1.2=-13.2. After could how many times it took to get to -12 and the add the 1/2 or 0.5. So your answer is 5.5 or B!
:)