**Core Concept**
The development of neck control is a significant milestone in a child's motor development, reflecting the maturation of the **central nervous system** and the integration of **musculoskeletal** functions. This milestone is crucial for further developmental achievements, such as sitting and walking.

**Why the Correct Answer is Right**
Typically, a child achieves complete neck control by around 4 months of age. This is because, by this age, the muscles of the neck have developed sufficiently to support the head against gravity, and the **cervical spine** has matured to allow for a range of motion. The development of neck control is also closely linked to the maturation of the **brainstem** and **cerebellum**, which are responsible for coordinating motor functions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it suggests an age that is too early for most children to have achieved complete neck control.
**Option B:** This option might seem plausible but is not the most accurate age for achieving complete neck control.
**Option D:** This option is incorrect because it suggests an age that is too late for the typical development of neck control in a normal child.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the acquisition of neck control is a precursor to other significant motor milestones, such as sitting up without support and eventually walking. Delays in achieving neck control can indicate **developmental delays** or **neuromuscular disorders**.

**Correct Answer:** Correct Answer: C. 4 months.