Respiratory trees are found in

Options

A. sea water
B. sea urchin
C. brittle star
D. sea cucumber

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks where respiratory trees are found. We need to identify the organism that possesses this structure.

2. **Identifying the Options**: The options provided are:
- Sea water
- Sea urchin
- Virgin star
- Sea cucumber

3. **Defining Respiratory Trees**: Respiratory trees are specialized structures that function in respiration. They are typically associated with the cloaca, which is an opening that serves multiple functions including excretion and respiration.

4. **Analyzing the Cloaca**: The cloaca is a common opening for the urinary, digestive, and reproductive tracts in certain animals. In the context of respiratory trees, they are branches that extend from the cloaca and are involved in gas exchange.

5. **Identifying the Correct Organism**:
- Sea urchins are known to have respiratory trees that help them in respiration by drawing in water and extracting oxygen.
- Sea cucumbers also have respiratory trees, but they are more commonly associated with the term "respiratory trees."
- Virgin star does not have respiratory trees.
- Sea water is not an organism, so it cannot be the answer.

6. **Conclusion**: Based on the information, the organism that possesses respiratory trees is the sea cucumber.

### Final Answer:
Respiratory trees are found in **sea cucumber**.