Respiratory structures in hemichordates are

Options

A. Trachea
B. Gills
C. Lungs
D. Ctenidia

Answer

### Step-by-Step Solution:

1. **Understanding Hemichordates**: Hemichordates are a unique group of animals that exhibit characteristics of both chordates and non-chordates. They are not fully classified as either group, which makes them interesting for study.

2. **Identifying Key Features**: Hemichordates possess a notochord, which is a characteristic feature of chordates. However, they lack a true nerve chord, which is typical of non-chordates. This combination of features is essential for understanding their classification.

3. **Respiratory Structures**: The primary respiratory structures in hemichordates are gills. These gills are used for respiration, allowing hemichordates to extract oxygen from water.

4. **Example of Hemichordates**: A well-known example of hemichordates is Balanoglossus, which is found in marine environments. This example helps illustrate the characteristics and respiratory structures of the group.

5. **Conclusion**: Therefore, the respiratory structures in hemichordates are gills, making the correct answer to the question about their respiratory structures clear.