The body part used to write is the Hand.

Explanation:
Writing is a skill that requires the use of various parts of the body, such as the eyes to see, the mouth to speak, and the feet to move around. However, the primary body part used to write is the hand. Here are some reasons why the hand is used to write:

1. Fine motor skills: Writing requires the use of fine motor skills, which are the small movements of the hand and fingers. These skills are essential for holding a pencil or pen and making precise movements to form letters and words.

2. Hand-eye coordination: Writing also requires hand-eye coordination, which is the ability to use the eyes to guide the movements of the hand. This coordination is necessary for writing neatly and accurately.

3. Brain-hand connection: Writing involves a connection between the brain and the hand. The brain sends signals to the hand, telling it what to write, and the hand responds by forming the letters and words.

4. Writing speed: Finally, the hand is used to write because it is the fastest body part for writing. While some people can type faster than they can write, handwriting is still a valuable skill that is used in many situations.

In conclusion, the hand is the primary body part used for writing because it requires fine motor skills, hand-eye coordination, a brain-hand connection, and is the fastest method of writing.