**Core Concept**
In medical jurisprudence, the concept of criminal responsibility in minors is governed by the principle of "doli incapax," which assumes that children under a certain age are incapable of committing a crime due to their lack of understanding and judgment.

**Why the Correct Answer is Right**
The age of majority, which marks the transition from minority to majority, varies across jurisdictions but is generally considered to be 18 years in most countries. At this age, an individual is presumed to have the capacity to understand the consequences of their actions and is held fully responsible for their crimes. This is based on the idea that individuals at this age have reached a level of cognitive and emotional maturity that enables them to make informed decisions and distinguish right from wrong.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify a universally accepted age of criminal responsibility. Different jurisdictions have varying ages, and this option lacks clarity.
* **Option B:** This option is incorrect because it implies an age that is too low to be considered the minimum age for criminal responsibility. Most jurisdictions consider children under this age to be incapable of committing crimes due to their immaturity.
* **Option C:** This option is incorrect because it suggests an age that is too high to be considered the minimum age for criminal responsibility. While 21 may be the age of majority in some jurisdictions, it is not the minimum age for criminal responsibility.

**Clinical Pearl / High-Yield Fact**
The concept of "doli incapax" is essential in medical jurisprudence, as it helps to balance the need for justice with the need to protect minors who may not fully understand the consequences of their actions.

**Correct Answer: C. 21**