Which of the phylum contains exclusively marine, radially symmetrical , diploblastic organisms with the tissue level organization ?

Options

A. Platyhelminthes
B. Ctenophora
C. Arthropoda
D. Annelida

Answer

To solve the question, we need to identify which phylum contains exclusively marine, radially symmetrical, diploblastic organisms with tissue-level organization. Let's break down the options provided:

1. **Platyhelminthes**:
- These are flatworms.
- They are triploblastic (not diploblastic) and bilaterally symmetrical.
- They have organ-level organization.
- **Conclusion**: Not the correct answer.

2. **Ctenophora** (also known as Comb Jellies or Sea Walnuts):
- They are exclusively marine.
- They exhibit radial symmetry.
- They are diploblastic and have tissue-level organization.
- They possess eight rows of ciliated comb plates for locomotion.
- **Conclusion**: This is a strong candidate for the correct answer.

3. **Arthropoda**:
- This phylum includes insects, arachnids, and crustaceans.
- They have an exoskeleton and a segmented body.
- They are triploblastic and bilaterally symmetrical.
- **Conclusion**: Not the correct answer.

4. **Annelida**:
- Known as segmented worms (e.g., earthworms, leeches).
- They are also triploblastic and bilaterally symmetrical.
- They have organ-level organization.
- **Conclusion**: Not the correct answer.

After analyzing all the options, we can conclude that the phylum that contains exclusively marine, radially symmetrical, diploblastic organisms with tissue-level organization is **Ctenophora**.

### Final Answer:
**Ctenophora**