Assertion. In bark all the cells are dead.
Reason. Bark constitutes secondary cortex, epidermis, cork etc.

Options

A. If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
B. If both Assertion and 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 and Reason are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "In bark all the cells are dead." This refers to the outer layers of a tree, which include the cork and other tissues that make up the bark.

2. **Analyzing the Reason**: The reason given is that "Bark constitutes secondary cortex, epidermis, cork, etc." This indicates that the bark is made up of various layers, including the cork (which is part of the bark).

3. **Identifying the Composition of Bark**:
- Bark is primarily composed of the cork (phellem), cork cambium (phellogen), and secondary cortex.
- The cork is the outermost layer and is known for being protective and insulating.

4. **Understanding Cell Viability**:
- The cells in the cork and the outer layers of the bark are indeed dead. This is because they have lost their protoplasm and are filled with suberin, a waxy substance that makes them impermeable to water and gases.
- The cork cells are formed from the cork cambium and are dead at maturity, serving as a protective barrier.

5. **Conclusion**: Since the assertion is that all cells in the bark are dead, and the reason provided explains the composition of the bark, we can conclude that both the assertion and the reason are correct.

### Final Answer:
Both the assertion and the reason are true, and the reason correctly explains the assertion.

---