**Core Concept**
Statutory rape refers to sexual intercourse between individuals where one party is below the legal age of consent. The legal age of consent varies by jurisdiction, but in most Indian legal systems, including the Indian Penal Code (IPC), the age of consent is 18 years. Thus, any sexual act with a person below 18 years is considered statutory rape, regardless of consent.

**Why the Correct Answer is Right**
Under Section 375 of the Indian Penal Code, sexual intercourse with a person below 18 years of age is defined as statutory rape. The law does not require proof of coercion or lack of consent; the mere fact that the individual is under 18 years of age constitutes a criminal offense. This age threshold is consistent across most legal frameworks in India and is a key principle in forensic medicine and criminal law.

**Why Each Wrong Option is Incorrect**
Option A: The age of 15 years is too low and not the legal threshold in Indian law.
Option B: 16 years is still below the statutory age of consent and may be relevant in some cases, but it is not the official cutoff.
Option D: 20 years exceeds the legal age of consent and does not define statutory rape.

**Clinical Pearl / High-Yield Fact**
In forensic medicine, the age of 18 years is the legal benchmark for consent in India. Any sexual act with a person under 18, regardless of consent, is a criminal offense under IPC Section 375. This principle applies even if the younger individual appears to consent.

✓ Correct Answer: C. Less than 18 years