Question

How many NOR gates are required to form NAND gate:
(A) $1$
(B) $2$
(C) $3$
(D) $4$

Answer 1

Hint
In these kinds of situations the first thing important is to notice the given problem statement. Specially this is a question with a little manipulation. To interpret we can either make a logic gate of can make the structure for the entire process. This will lead to security regarding the answers.

Complete step by step answer

This is a typical example of a NAND gate.
Now, $4$ gates are essential to form NAND gates.
For Input:
For input it is important to have $2$ NOR gates. These should be single inputs for input.
For Output:
For input it is important to have $1$ NOR gates. These should be multiple connected inputs for output.
For Conversion:
For this we need $1$ NOR gate. The role of this gate is to convert AND to NAND.
Option (D) is correct.

Note
Most important thing here is to notice the given options and then we can easily emulate the right answer even if we are unaware of it. Apart from that it is clear that the first approach should be solving and obtaining answers so that we can be sure.