Infertility means:

The correct answer is Option (4) → Inability to conceive or produce children even after 2 years of unprotected sex

Infertility means that a couple cannot have a child even after a fixed period of trying. NCERT fixes this period at 2 years of unprotected sexual cohabitation. Methods such as In Vitro Fertilisation (IVF) are used to help such couples.

(1) Inability to conceive or produce children even after 4 years of unprotected sex — Incorrect. The period is 2 years, not 4.

(2) Inability to conceive or produce children even after 3 years of unprotected sex — Incorrect. The period is 2 years, not 3.

(3) Ability to conceive or produce children even after 2 years of unprotected sex — Incorrect. This describes fertility, the opposite of infertility. Infertility is the inability.

(4) Inability to conceive or produce children even after 2 years of unprotected sex — Correct. It gives both the inability and the correct period.

NCERT Extract:
Infertility – …