## **Core Concept**
The developmental milestone of knowing one's full name is an important indicator of cognitive and language development in children. This skill is typically acquired as part of a child's growing vocabulary and understanding of personal identity. Pediatric guidelines often provide age ranges for achieving such milestones.

## **Why the Correct Answer is Right**
By the age of **2 years**, children often start to develop a sense of self and may begin to identify themselves by name. Knowing one's full name is a complex piece of information that requires memory and cognitive ability to understand and recall. At around 2 years old, children's vocabularies expand significantly, and they start to use personal pronouns and refer to themselves by name.

## **Why Each Wrong Option is Incorrect**
* **Option A:** Typically, knowing one's full name by **1 year** is early for most developmental milestones. At 1 year, children are just beginning to say a few words and may not have a consistent way to refer to themselves.
* **Option B:** While some children might start to learn their full name around **1.5 years**, consistently knowing and recalling it might still be challenging for many at this age.
* **Option D:** By **3 years**, most children can indeed identify themselves by their full name, but this is slightly later than the typical age by which they first acquire this knowledge.

## **Clinical Pearl / High-Yield Fact**
A useful clinical pearl to remember is that by **2 years** of age, children are expected to:
- Use around 50 words and start combining two words together.
- Identify major body parts when asked.
- Start to show an understanding of personal identity, such as knowing their first and last name.

## **Correct Answer:** C. 2 years.