**Core Concept**
The question tests the understanding of **neurodevelopmental milestones** and **gastrointestinal physiology**, specifically the age at which children develop control over their bowel movements. This is related to the maturation of the **central nervous system** and the development of **voluntary sphincter control**.

**Why the Correct Answer is Right**
By around 2-3 years of age, most children have developed sufficient **cortical control** over their bowel movements to be able to withhold and postpone them. This is a key milestone in **toilet training** and indicates a level of neurological maturity. The ability to control bowel movements is closely linked to the development of the **anus** and the **rectum**, as well as the **nervous system**.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is too early for most children to have developed this level of control.
**Option B:** This option might seem plausible but is not the most accurate age.
**Option D:** This option is too late, as most children should have achieved this milestone earlier.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the ability to control bowel movements is a critical aspect of **toilet training** and **pediatric development**. Failure to achieve this milestone can indicate **neurodevelopmental delays**.

**Correct Answer:** Correct Answer: C. 2-3 years.