Question

Digital circuit can be made by repetitive use of this gate-
(A) AND
(B) OR
(C) NOT
(D) NAND

Answer 1

Hint To find the correct question, you first need to realize that the options contain three basic logic gates while the fourth one is a bit complex. Other than that, you must have witnessed that we have used NAND and NOR gates a lot for creation of different kinds of circuits, hence, the answer must stand out to you now out of the given four options.

Complete step by step answer
As explained in the hint section of the solution to the asked question, if we have a look at the given options, three logic gates, namely AND, OR and NOT are the basic generic logic gates while the fourth option, NAND logic gate is a complex gate and we must have already witnessed multiple times NAND and NOR gates being used to create different kinds of logic gates, like XOR and XNOR logic gates, and circuits.
Also, as told in the study materials, NAND gate is also called universal gate. It is so because every other logic gate like AND, OR and NOT can be synthesized from various multiple combinations and setups of NAND gates alone. If NAND gates can basically replace all of the other logic gates, we can confidently say that any or every digital circuit that needs to be constructed can easily be constructed using NAND gates repetitively.

Hence, we can see that the correct answer to the question is nothing but option (D), NAND gate.

Note Many students skip the creation of other logic gates using NAND or NOR gates and thus either tick a wrong option or skip such questions while if you study the creation of other logic gates using NAND or NOR gates alone, this will gain you easy quick marks in any exam.