Which of the following organisms is radially symmetrical?

Options

A. Pila
B. Echinus
C. Cucumaria
D. Both (B) and (C )

Answer

To determine which of the following organisms is radially symmetrical, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Radial Symmetry**:
- Radial symmetry is a body plan in which an organism can be divided into similar halves by passing a plane through its central axis at any angle. This means that the organism has a circular or cylindrical shape, allowing for multiple lines of symmetry.

2. **Evaluate the Options**:
- We need to analyze each option provided in the question to see if they exhibit radial symmetry.

3. **Option A - Pylons**:
- Pylons are typically associated with organisms that show bilateral symmetry, meaning they can only be divided into two similar halves along one plane. Thus, this option is incorrect.

4. **Option B - Echinus**:
- Echinus, commonly known as sea urchins, exhibit radial symmetry. If you draw lines through the center of a sea urchin, you can see that it can be divided into similar halves at multiple angles. Therefore, this option is correct.

5. **Option C - Cucumeria**:
- Cucumeria, which refers to certain types of sea cucumbers, also shows radial symmetry. Similar to Echinus, it can be divided into similar halves along multiple planes. Thus, this option is also correct.

6. **Option D - Both B and C**:
- Since both Echinus and Cucumeria exhibit radial symmetry, this option is correct as well.

7. **Conclusion**:
- The correct answer is option D, which states that both Echinus and Cucumeria are radially symmetrical organisms.

### Final Answer:
- The organism that is radially symmetrical is **Option D: Both B and C (Echinus and Cucumeria)**.