From the prime implicant chart we can say 2 expressions possible for the given boolean function
Exp 1:AC+A'C'+B
Exp 2:AC+A'C'+A'B'+AB'
The number of literals for Exp 1 is less than Exp 2 .
So we consider Exp 1, for which we have 3 implicants.
OPTION B is the answer.