## **Core Concept**
The question assesses the developmental milestones of infants, specifically focusing on the age at which an infant can hold its head steady when pulled to a sitting position and exhibits laughter. This involves understanding the typical **gross motor skills** and **cognitive or emotional development** milestones.

## **Why the Correct Answer is Right**
Infants typically achieve certain developmental milestones within specific age ranges. Holding the head steady when pulled to sit, without a bobbing motion, and laughing loudly are significant milestones.
- **Holding the head steady** indicates improved **neck muscle strength** and **neurological development**.
- **Laughing loudly** is a sign of **cognitive and emotional development**, reflecting the infant's ability to experience joy and express it.

These milestones are usually achieved around **6 months of age**. At this stage, infants have developed sufficient neck and back muscle strength to support their head and upper body when pulled to a sitting position. They also start to exhibit more complex emotional responses, such as laughter.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Typically, infants start to show some head control and may begin to laugh but not as consistently or loudly as at 6 months.
- **Option B:** Around this age, infants are just beginning to discover their hands and may not have achieved the described milestones.
- **Option D:** By this age, infants usually have achieved more advanced milestones, such as sitting without support and possibly starting to show interest in solid foods.

## **Clinical Pearl / High-Yield Fact**
A key developmental milestone to remember is that by **6 months**, infants should be able to hold their head steady when pulled to a sit and exhibit social smiles and laughter. Pediatricians assess these milestones during routine check-ups to ensure proper development.

## **Correct Answer:** C. 6 months.