Concept:
Child marriage is prohibited in India under the Prohibition of Child Marriage Act because it negatively affects the physical, mental, reproductive, and social health of girls.
Early marriage may lead to:
• Early pregnancy
• Increased maternal and infant health risks
• High fertility rate
• Poor educational and social outcomes
Step 1: Analyze Assertion (A).
Child marriage is illegal in India and is considered a punishable offence under the law.
Hence, Assertion (A) is correct.
Step 2: Analyze Reason (R).
The age at marriage significantly influences fertility and reproductive health of girls. Early marriage is associated with higher fertility and health complications.
Hence, Reason (R) is correct.
Step 3: Check whether Reason explains Assertion.
Since early marriage affects reproductive health and fertility, it forms one of the important reasons for prohibiting child marriage.
Therefore, Reason (R) is the correct explanation of Assertion (A).
Hence, the correct answer is:
\[
\boxed{(A)\ \text{Both (A) and (R) are correct and (R) is the correct explanation of (A)}}
\]