Assertion : The endoplasmic reticullum which lacks ribosomes is called smooth endoplasmic reticulum (SER).
Reason : SER is mainly involved in protein synthesis.

Options

A. If both assertion and reason are true amnd 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

To analyze the given assertion and reason, we will break down the information step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the endoplasmic reticulum (ER) which lacks ribosomes is called the smooth endoplasmic reticulum (SER).
- This statement is **true**. The SER is characterized by the absence of ribosomes on its surface.

2. **Understanding the Reason**:
- The reason provided states that the SER is mainly involved in protein synthesis.
- This statement is **false**. The SER is primarily involved in lipid synthesis, including steroid hormones, and detoxification processes. Protein synthesis occurs mainly in the rough endoplasmic reticulum (RER), which has ribosomes attached to its surface.

3. **Conclusion**:
- Since the assertion is true and the reason is false, we conclude that the correct relationship between the assertion and reason is that the assertion is correct, but the reason is incorrect.

### Final Answer:
- The assertion is true, and the reason is false.