$ The biomembrane which surrounds a vacuole is called Tonoplast.
! Ribosomes have a plasma membrane.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion:**
- The assertion states that "the biomembrane which surrounds a vacuole is called tonoplast."
- A vacuole is a membrane-bound organelle found in cells, primarily in plant cells, where it serves various functions including storage of substances.

2. **Verifying the Assertion:**
- The tonoplast is indeed the membrane that surrounds the vacuole. It is responsible for maintaining the internal environment of the vacuole and regulating the movement of ions and molecules in and out of it.
- Therefore, the assertion is **correct**.

3. **Understanding the Reason:**
- The reason states that "ribosomes have a plasma membrane."
- Ribosomes are cellular structures that synthesize proteins and are known to be **membrane-less**.

4. **Verifying the Reason:**
- Ribosomes can either be free-floating in the cytoplasm or attached to the endoplasmic reticulum (ER), but they do not possess a plasma membrane.
- Therefore, the reason is **incorrect**.

5. **Conclusion:**
- Since the assertion is correct and the reason is incorrect, the final evaluation is that the assertion is true while the reason is false.

**Final Answer:**
- The assertion is correct, and the reason is incorrect.

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