$(A'BC')'+(AB'C)'\\=\left\{(A')'+B'+(C')'\right\}+\left\{A'+(B')'+C'\right\};~[\text{Applying De Morgan's law}]\\=A+B'+C+A'+B+C';~[\because (X')'=X]\\=(A+A')+(B+B')+(C+C');~[\text{Commutative and Associtive laws}]\\=1+1+1;~[\because X+X'=1 \text{ as the Complement law}]\\=1;~[\because 1+1=1 \text{ in Boolean algebra}]$
So the correct answer is B.