**Question:** A 4-year-old child can perform one of the following:

a) Can hop on one leg for 15 feet
b) Can skip without falling to either side
c) Can stand on one foot for 20 seconds
d) Can walk down the stairs with alternating steps, holding on to the iron rail

**Correct Answer:**

**Core Concept:** Developmental milestones refer to the expected achievements in physical and cognitive abilities during childhood. These milestones serve as a guideline to assess a child's overall development and identify any potential delays or disorders. In the given options, we are evaluating children's motor skills.

**Why the Correct Answer is Right:**

At the age of 4, children develop various motor skills, including balance, coordination, and strength. The correct answer refers to a child's ability to demonstrate an advanced motor skill:

1. **Option D (Walking down the stairs with alternating steps, holding on to the iron rail):** At 4 years old, a child typically develops the motor skills required for safe stair climbing, including balance and coordination. Holding on to the rail provides stability and safety. Walking down the stairs with alternating steps signifies the child's ability to coordinate their leg movements and maintain balance, a crucial milestone for a 4-year-old.

2. **Option C (Standing on one foot for 20 seconds):** At this age, children can hold their balance for a few seconds, which is an essential step towards developing the ability to stand on one foot for longer durations and perform more complex motor tasks.

3. **Option B (Skipping without falling to either side):** At 4 years old, children develop the ability to jump, which is a precursor to skipping. Skipping without falling to either side indicates a child's improved coordination and balance.

4. **Option A (Hopping on one leg for 15 feet):** While a 4-year-old can hop on one leg, the distance (15 feet) is not a typical milestone for this age group. The focus should be on the basic motor skills (skipping or hopping) rather than the distance achieved.

**Why Each Wrong Answer is Incorrect:**

1. **Option A (Hopping on one leg for 15 feet):** As mentioned above, focusing on distance is not relevant for this age group. A 4-year-old should be evaluated based on their ability to hop on one leg rather than distance achieved.

2. **Option B (Skipping without falling to either side):** While children can jump at this age, focusing on falling to either side is not a typical milestone for a 4-year-old. The evaluation should concentrate on basic motor skills, such as jumping or hopping, rather than the ability to fall to either side.

3. **Option C (Standing on one foot for 20 seconds):** A 4-year-old may not have the necessary balance and coordination to hold a position for 20 seconds on one leg. Instead, the focus should be on the ability to hold a position for