Okay, let's tackle this question. The question is about when a child reaches a height of 100 cm. Hmm, I remember that growth patterns are important in pediatric assessments. Let's think about the average growth milestones.

First, I know that at birth, the average height is around 50 cm. By the first birthday, they usually double in length, so about 75 cm. Then, the growth rate slows down. By age 2, they might be around 85-90 cm. Wait, but the question is about 100 cm. So when do they reach that?

I recall that by the age of 4 years, the average height is about 100 cm. Let me verify. Growth charts from WHO or CDC can be a reference. The WHO growth standards for boys and girls show that at 4 years old, the median height is approximately 100 cm. So that would be the correct answer here.

Now, the options are A to D, but the user didn't list them. But since the correct answer is 4 years, I need to explain why that's the case. The core concept here is the normal growth curve in children. The key points are the rapid growth in the first year, slowing down in the second, and then steady growth until puberty.

Why is 4 years the right answer? Because the growth velocity decreases after the first year, but cumulative growth by age 4 adds up to about 100 cm. The calculation is based on average growth rates: about 25 cm in the first year, 10-12 cm in the second, and then about 6-7 cm per year until puberty. So adding those up: 50 cm at birth + 25 cm (year 1) = 75 cm, +12 cm (year 2) = 87 cm, +7 cm (year 3) = 94 cm, +6 cm (year 4) = 100 cm.

The wrong options would be earlier ages. For example, if an option says 3 years, that's around 94 cm. If an option is 5 years, that would be around 107 cm. So those would be incorrect.

Clinical pearl: Remember that by age 2, a child's height is about three times the birth length. By 4 years, it's roughly 100 cm. This is a key milestone for pediatricians to assess growth and development. Also, deviations from these norms can indicate growth disorders or other health issues.

So the correct answer is 4 years old. The user's options probably had 4 years as one of the choices, like option C or D. But since the user didn't provide the options, I'll proceed with the explanation based on the correct answer being 4 years.

**Core Concept**
This question tests knowledge of normal pediatric growth patterns. A child's height increases progressively, with rapid growth in early years and slower gains later. Growth milestones are critical for assessing developmental health and identifying growth disorders.

**Why the Correct Answer is Right**
The average child reaches 100 cm (1 meter) in height by **4 years of age**. Birth height (~50 cm) doubles by 1 year (75 cm), triples

✓ Correct Answer: C. 4-5 years