Answer: A. NAND gate
The circuit is equivalent to a NAND gate
In the above circuit, In the first stage the inputs A&B are given to a NAND gate, then its output is fed to a NOT gate (that is constructed using a NOR gate), and again its output is given to a NOT gate, so the output Y must be same that of a NAND gate.
The circuit is equivalent to a NAND gate.
option A is the correct answer.