The sex chromosome of a female bird has -

The correct answer is Option (3) → ZW

In birds the female makes two kinds of eggs with respect to the sex chromosomes (female heterogamety). The two different sex chromosomes of the female are named Z and W, and the male has a pair of Z chromosomes.

Option (3) ZW — Correct. In birds, sex is determined by the female. The female is heterogametic, with Z and W sex chromosomes, while the male is homogametic with ZZ.

Note: A similar question was also asked in CUET (UG) 2025 on 16-05-2025 (Slot 1).

NCERT Extract:
Sex Determination – “… In some other organisms, e.g., birds, a different mechanism of sex determination is observed (Figure 4.12 c). In this case the total number of chromosome is same in both males and females. But two different types of gametes in terms of the sex chromosomes, are produced by females, i.e., female heterogamety. In order to have a distinction with the mechanism of sex determination described earlier, the two different sex chromosomes of a female bird has been designated to be the Z and W chromosomes. In these organisms the females have one Z and one W chromosome, whereas males have a pair of Z-chromosomes besides the autosomes.”