The logic circuit performs the logic function of:

The correct answer is Option (3) → OR

A NOR gate gives the complement of A + B. When both inputs of a NOR gate are joined, it acts as a NOT gate, because \( \overline{Y' + Y'} = \overline{Y'} \).

The first gate is a NOR gate with inputs A and B:

    \( Y' = \overline{A + B} \)

The second gate is a NOR gate with both inputs tied to \( Y' \), so it inverts \( Y' \):

    \( \displaystyle Y = \overline{Y' + Y'} = \overline{Y'} = \overline{\overline{A + B}} = A + B \)

So the circuit gives Y = A + B, the OR function.

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):
Logic Gates – “… It has two or more inputs and one output. A NOT- operation applied after OR gate gives a NOT-OR gate (or simply NOR gate). Its output Y is ‘1’ only when both inputs A and B are ‘0’, i.e., neither one input nor the other is ‘1’. The symbol and truth table for NOR gate is given in Fig. 14.42.

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).”