## Core Concept
The question assesses the understanding of growth parameters in children, specifically the relationship between height, weight, and age. It requires knowledge of standard growth charts and expected growth patterns in healthy children.

## Why the Correct Answer is Right
To determine the most likely age of the child, we refer to standard growth charts, which typically plot height and weight against age. For a child with a height of 100 cm and a weight of 16 kg, we can estimate their age based on average growth milestones. Generally, at around 5 years of age, a child is expected to be approximately 100-110 cm tall and weigh around 15-18 kg. Therefore, a child with a height of 100 cm and a weight of 16 kg is most likely around **5 years old**.

## Why Each Wrong Option is Incorrect
- **Option A:** 2 years old. At 2 years, a typical child is about 85-90 cm tall and weighs around 12 kg, which does not match the given parameters.
- **Option B:** 3 years old. A 3-year-old child usually measures around 95 cm in height and weighs approximately 14 kg, still not aligning with the provided measurements.
- **Option D:** 7 years old. A child of 7 years typically has a height of around 120 cm and weighs about 20-25 kg, which is significantly more than the given measurements.

## Clinical Pearl / High-Yield Fact
A useful clinical pearl is to remember that, on average, a child's height increases by about 5-6 cm per year and their weight by approximately 2 kg per year after the age of 2. This rough estimation can help in quickly assessing a child's growth pattern.

## Correct Answer Line
**Correct Answer: C. 5 years.**