Radial symmetry is usually exhibited in animals which

Options

A. Have one opening of alimentary canal
B. Live in water
C. Have ciliary mode of feeding
D. are attached to the substratum

Answer

To answer the question "Radial symmetry is usually exhibited in animals which," we need to analyze the options provided and understand the concept of radial symmetry.

### Step-by-Step Solution:

1. **Understanding Radial Symmetry**:
- Radial symmetry is a form of symmetry where the body parts are arranged around a central axis. This means that if you were to slice the organism through the center, each slice would be similar in shape and structure.

2. **Identifying Characteristics of Radial Symmetry**:
- Animals with radial symmetry typically have a body structure that allows them to interact with their environment from all directions. This is common in aquatic animals.

3. **Analyzing the Options**:
- **Option 1: Have one opening of the elementary canal**: This is not a defining characteristic of radial symmetry. Many animals with bilateral symmetry also have one opening.
- **Option 2: Live in water**: Many animals that exhibit radial symmetry, such as jellyfish and starfish, are indeed aquatic. This option aligns with the characteristics of radial symmetry.
- **Option 3: Have ciliary mode of feeding**: While some radially symmetrical animals may use cilia for feeding, this is not a universal trait for all animals with radial symmetry.
- **Option 4: Are attached to the substratum**: Some radially symmetrical animals may be sessile (attached), but not all exhibit this trait.

4. **Conclusion**:
- The most accurate option that describes animals exhibiting radial symmetry is **Option 2: Live in water**. This is because most radially symmetrical animals are marine and have adaptations that allow them to feed from all directions in their aquatic environment.

### Final Answer:
Radial symmetry is usually exhibited in animals which **live in water**.

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