Assertion : We are able to move a few parts of our body easily in various directions whereas some parts can be moved in only one direction.
Reason : Different types of joints are present in different parts of our body.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that we can move some parts of our body in various directions while others can only move in one direction. This is true because different joints allow for different ranges of motion. For example, our shoulder allows for a wide range of movement (like a ball and socket joint), while our elbow primarily allows for bending and straightening (like a hinge joint).

2. **Understanding the Reason**: The reason provided explains that different types of joints are present in different parts of our body. This is also true. There are several types of joints in the human body, including ball and socket joints, hinge joints, pivot joints, etc., each allowing for different types of movement.

3. **Evaluating the Relationship**: Now we need to determine if the reason correctly explains the assertion. The reason does explain why the assertion is true: the type of joint determines the range of motion. Therefore, the reason supports the assertion.

4. **Choosing the Correct Option**: Since both the assertion and the reason are true, and the reason correctly explains the assertion, the correct option is A: "If both assertion and reason are true and reason is the correct explanation of assertion."