[A]: In certain plants the stem that twins around the support is hard and woody, such plants are called psammophytes.
[R]: The hygroscopic roots have a spongy tissue called exodermis

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states: "In certain plants, the stem that twines around the support is hard and woody; such plants are called psammophytes."

- **Understanding Psammophytes**: Psammophytes are plants that thrive in sandy environments, particularly in deserts. They have adaptations to survive in shifting sands, such as reduced leaves or a thick cuticle to prevent water loss. The assertion incorrectly describes psammophytes as plants with woody stems that twine around supports, which is not characteristic of them.

### Step 2: Analyze the Reason
The reason states: "The hygroscopic roots have a spongy tissue called exodermis."

- **Understanding Hygroscopic Roots**: Hygroscopic roots are specialized roots that can absorb moisture from the air. The spongy tissue that aids in this absorption is not called exodermis; it is actually known as "velamen." The exodermis is a layer of cells in roots that helps in the regulation of water and nutrient uptake, but it is not specifically associated with hygroscopic roots.

### Step 3: Conclusion
Based on the analysis:
- The assertion is false because it mischaracterizes psammophytes.
- The reason is also false because it incorrectly identifies the tissue associated with hygroscopic roots.

### Final Answer
Both the assertion and the reason are false.