**Core Concept**
The development of neck control in infants is an essential milestone in motor skills acquisition. It involves the maturation of the muscles of the neck, particularly the sternocleidomastoid and trapezius, as well as the integration of sensory and motor inputs from the cervical spine and cranial nerves.

**Why the Correct Answer is Right**
The ability to control the neck, also known as neck righting or head control, typically develops around 4-6 months of age. This is achieved through the maturation of the sternocleidomastoid muscle, which helps to stabilize the head, and the development of the cervical spine, which allows for greater flexibility and control. As the child gains neck control, they are able to hold their head up while in a sitting position and eventually move it from side to side.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a correct age range for the development of neck control.
**Option B:** This option is incorrect because it does not provide a clear definition of when neck control is acquired.
**Option C:** This option is incorrect because it implies that neck control is acquired in a specific position, rather than as a developing skill.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the development of neck control is a gradual process that occurs over several months, and it's a crucial milestone in the overall development of motor skills in infants.

**Correct Answer: D. 6 months**