Assertion:- Smooth endoplasmic reticulum is frequently observed in protein secretory cells.
Reason:- Lumen of smooth endoplasmic reticulum is the only storage site of secretory proteins.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are false.

Answer

### Step-by-Step Solution

1. **Understanding the Assertion**: The assertion states that "Smooth endoplasmic reticulum is frequently observed in protein secretory cells."
- The smooth endoplasmic reticulum (SER) is primarily involved in lipid synthesis and detoxification processes, not in protein synthesis. Therefore, this assertion is incorrect.

2. **Understanding the Reason**: The reason given is "Lumen of smooth endoplasmic reticulum is the only storage site of secretory proteins."
- The lumen of the rough endoplasmic reticulum (RER) is where secretory proteins are synthesized and stored, not the SER. Thus, this reason is also incorrect.

3. **Conclusion**: Since both the assertion and the reason are false, we conclude that the correct answer is that both the assertion and the reason are false statements.

4. **Final Answer**: Therefore, the answer to the question is that both the assertion and reason are false.