To get an output Y = 1 from the circuit shown below, the input must be
a = 1, b = 0, c = 0
a = 0, b = 1, c = 0
a = 0, b = 0, c = 1
a = 1, b = 0, c = 1
To get an output of 1, from the NAND gate
both input should be 1.
C = 1
Now Resultant of a & b should be 1.
So the Correct option is 4.