If two bodies stick together after collision and move as a single body, the collision is said to be

Options

A. perfectly inelastic
B. elastic
C. inelastic
D. perfectly elastic.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Collision Types**:
- In physics, collisions can be classified into different types based on the behavior of the bodies involved after the collision. The two main types are elastic and inelastic collisions.

2. **Identifying the Given Condition**:
- The question states that two bodies stick together after the collision and move as a single body. This indicates that they do not separate after colliding.

3. **Defining Perfectly Inelastic Collision**:
- A perfectly inelastic collision is a specific type of inelastic collision where the two colliding bodies stick together and move with a common velocity after the collision.

4. **Coefficient of Restitution**:
- In a perfectly inelastic collision, the coefficient of restitution (denoted as 'e') is equal to zero. This means that there is no relative motion between the two bodies after the collision.

5. **Conclusion**:
- Based on the definition and the condition provided in the question, we conclude that if two bodies stick together after a collision and move as a single body, the collision is termed a **perfectly inelastic collision**.

**Final Answer**: The collision is said to be a **perfectly inelastic collision**.

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