**Core Concept**
The question tests the knowledge of pediatric growth and development, specifically the attainment of a certain height at a particular age. This is based on the understanding of **growth charts** and **percentiles** used in pediatrics.

**Why the Correct Answer is Right**
A child typically attains a height of 100 cms around the age of 4 years, as per the standard **growth charts**. This is because, on average, a child grows about 10 cms per year during the first few years of life, with the growth rate slowing down thereafter. The **growth hormone** plays a crucial role in regulating this growth.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it suggests an age that is too early for a child to reach 100 cms.
**Option B:** This option might seem plausible but is not the correct answer based on standard growth charts.
**Option D:** This option is incorrect because it suggests an age that is too late for a child to reach 100 cms.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that growth patterns can vary significantly among children, and **genetic factors** play a significant role.

**Correct Answer:** C. 4 years.