the correct ans is A bcz in xor gate when one input is 0 that implies A=0 or 1 the output of xor gate is 0 when both i/p's are same and one when any one of the input is high i.e., 00=0,01=1,11=0 and 10=1 here they gave that one input is 0 when A=0 both the inputs become 0 and the output is 0 when A=1 inputs become 01=1 the output is same as the input A