Organ level of organisation is present in the members of 

Options

A. Nematoda
B. Cnidaria
C. Platyhelminthes
D. Annelida

Answer

To determine which group of organisms exhibits organ level organization, we can analyze the options given: Nematoda, Cnidaria, Platyhelminthes, and Annelida.

### Step-by-Step Solution:

1. **Understanding Organ Level Organization**:
- Organ level organization refers to a biological structure where different tissues come together to form organs that perform specific functions.

2. **Analyzing Nematoda**:
- Nematodes (roundworms) have a more complex structure than simple tissues; they exhibit organ system level organization. Thus, they do not fit the criteria for organ level organization.

3. **Analyzing Cnidaria**:
- Cnidarians (like jellyfish and corals) display tissue level organization, where cells are organized into tissues but not into true organs. Therefore, this option is also incorrect.

4. **Analyzing Platyhelminthes**:
- Platyhelminthes (flatworms) demonstrate organ level organization. They possess organs that are formed from different types of tissues working together. This makes Platyhelminthes the correct answer.

5. **Analyzing Annelida**:
- Annelids (segmented worms) also exhibit organ system level organization, which is more complex than organ level organization. Thus, this option is incorrect as well.

### Conclusion:
Based on the analysis, the correct answer is **Platyhelminthes**, as they are the only group listed that exhibits organ level organization.