The following configuration of gate is equivalent to

Output of  G1=A+B; Output of  G2=A.B¯=A +B           Output of G3=A+B.A.B¯=A+B.A¯+B¯      ∵A.B¯=A¯+B¯​=A.A¯+A.B¯+B.A¯+B.B¯​=0+A.B¯+B.A¯+0=A.B¯+B.A¯  which gives XOR gate.   Output of  XOR gate is A.B¯+A¯.B  Therefore, the correct answer is (B).