Select the correct statement from the following:
A. Fleshy cylindrical stem in Euphorbia carries out photosynthesis.
B. Pistia and Eichhornia are examples of offset.
C. Underground stem of grass and strawberry spread to new niche and when older part die new plants are formed.
D. Thorns are woody, straight and pointed.

Options

A. A and B only
B. B and D only
C. B and C only
D. All of these

Answer

To solve the question, we need to evaluate each of the statements provided and determine which one is correct.

### Step-by-Step Solution:

1. **Evaluate Statement A:**
- Statement: "Fleshy cylindrical stem in Euphorbia carries out photosynthesis."
- Analysis: Euphorbia, a genus of flowering plants, often has fleshy stems that contain chlorophyll, allowing them to perform photosynthesis. Therefore, this statement is **correct**.

2. **Evaluate Statement B:**
- Statement: "Pistia and Eichhornia are examples of offset."
- Analysis: Both Pistia (water lettuce) and Eichhornia (water hyacinth) reproduce asexually through offsets, which are small daughter plants that grow from the parent plant. Thus, this statement is **correct**.

3. **Evaluate Statement C:**
- Statement: "Underground stem of grass and strawberry spread to new niche and when older part die new plants are formed."
- Analysis: Grass and strawberry plants utilize underground stems (like rhizomes) to spread to new areas. When the older parts die, new plants can indeed form from these underground structures. Therefore, this statement is **correct**.

4. **Evaluate Statement D:**
- Statement: "Thorns are woody, straight and pointed."
- Analysis: Thorns are indeed modified stems that are typically woody, straight, and pointed, serving as a defense mechanism for plants. This statement is also **correct**.

### Conclusion:
Since all four statements (A, B, C, and D) are correct, the correct answer to the question is **option 4: all of these**.