Which of the following gates can give an AND gate by its repetitive u…

The correct answer is Option (1) → Both NAND gate and NOR gate

NAND and NOR are called universal gates: by using either one of them repeatedly, every basic gate (NOT, OR, AND) can be built.

With NAND gates: a NAND followed by a NAND with its inputs joined (which acts as NOT) gives \( \overline{\overline{A\cdot B}} = A\cdot B \).

With NOR gates: two NOR gates with inputs joined give \( \bar{A} \) and \( \bar{B} \), and a third NOR gives \( \overline{\bar{A} + \bar{B}} = A\cdot B \) (De Morgan's theorem).

Option (1) Both NAND gate and NOR gate — Correct. Both universal gates can produce AND, as shown above.

Option (2) NOT gate only — Incorrect. A NOT gate has only one input, so NOT gates alone can never combine two inputs into an AND.

Option (3) OR gate only — Incorrect. Joining OR gates only gives OR of more inputs; OR is not a universal gate and cannot produce AND.

Option (4) NAND gate only — Incorrect. NAND can give AND, but NOR can as well, so "only" makes this option wrong.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
NAND Gate – “… NAND gates are also called Universal Gates since by using these gates you can realise other basic gates like OR, AND and NOT (Exercises 14.16 and 14.17).”

NOR Gate – “… NOR gates are considered as universal gates because you can obtain all the gates like AND, OR, NOT by using only NOR gates (Exercises 14.18 and 14.19).”