## **Core Concept**
Thumb sucking is a common habit in children, often seen as a self-soothing behavior. It is a type of **non-nutritive sucking behavior**, which also includes pacifier use. This behavior is particularly prevalent in early childhood.

## **Why the Correct Answer is Right**
The correct answer, **33%**, reflects the prevalence of thumb sucking in preschool children. Studies have shown that thumb sucking is a common habit in young children, with various factors contributing to its occurrence, including **psychological factors**, **habit formation**, and possibly **orthodontic issues**. The prevalence rates can vary, but 33% is a reasonable estimate for preschool-aged children.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it suggests a much lower prevalence than what is typically observed in preschool children.
- **Option B:** Similarly, this option underestimates the prevalence of thumb sucking in the specified age group.
- **Option D:** This option overestimates the prevalence, as while thumb sucking is common, it is not as high as suggested here for preschool children.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that thumb sucking can lead to **orthodontic problems** if the habit persists beyond early childhood, such as **malocclusion** and **protrusion of the upper incisors**. Pediatricians and dentists often advise parents on strategies to discourage this habit in children.

## **Correct Answer:** C. 33%