## **Core Concept**
Neck control, or the ability to hold one's head up while on the stomach, is a significant developmental milestone in infants. It is primarily associated with the strengthening of the **sternocleidomastoid** and other neck muscles. This milestone is crucial for further physical development.

## **Why the Correct Answer is Right**
The correct answer, , indicates that neck control is typically achieved by 4 months of age. This is because, by around 4 months, infants have developed sufficient strength in their neck muscles to support their head while on their stomach. This development is a part of the normal **motor skill** progression in infants.

## **Why Each Wrong Option is Incorrect**
* **Option A:** This age is too early for typical neck control development. Most infants are not developmentally ready for this milestone by 1 month.
* **Option B:** While some infants might start showing signs of neck control around 2 months, it is generally considered early for full neck control.
* **Option D:** This option suggests 6 months, which is later than the typical age for achieving neck control. Most infants have already achieved this milestone by this age.

## **Clinical Pearl / High-Yield Fact**
A useful clinical correlation to remember is that by 1 month, infants can usually lift their head while on their stomach but might not sustain it. By 2 months, they can sustain their head lift for a few seconds. **Neck control is usually achieved by 4 months**, and significant delay might indicate a neurological issue.

## **Correct Answer: .**