Indentify the phylum X
`"Animalia"rarr"Tissue Grade"rarr"Bilateral"rarr"Acoelomate"-X`

Options

A. Ctenophora
B. Platyhelminthes
C. Aschelminthes
D. Hemichordata.

Answer

To identify the phylum X given the characteristics "Animalia" → "Tissue Grade" → "Bilateral" → "Acoelomate", we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Kingdom**:
- The question starts with "Animalia", which indicates that we are dealing with animals.

2. **Determine the Level of Organization**:
- The next characteristic is "Tissue Grade". This means that the organisms in this phylum have tissues but not organs. This rules out phyla that have organ-level organization.

3. **Assess Symmetry**:
- The next characteristic is "Bilateral". This indicates that the organisms have bilateral symmetry, meaning they can be divided into two equal halves along one plane.

4. **Evaluate Body Cavity**:
- The final characteristic is "Acoelomate", which means that the organisms do not have a body cavity (coelom).

5. **Analyze the Options**:
- The options provided are:
- Ctenophora
- Platyhelminthes
- Acoelomorpha
- Hemichordata

6. **Compare Each Option**:
- **Ctenophora**: They have a tissue grade organization, bilateral symmetry, but they are not acoelomate; they have a body cavity.
- **Platyhelminthes**: They have a tissue grade organization, bilateral symmetry, and they are acoelomate. This fits all the criteria.
- **Acoelomorpha**: They are also acoelomate and have bilateral symmetry, but they are not typically classified under the tissue grade.
- **Hemichordata**: They have organ-level organization and a true coelom, which does not fit the criteria.

7. **Conclusion**:
- The only phylum that fits all the criteria of "Tissue Grade", "Bilateral", and "Acoelomate" is **Platyhelminthes**.

### Final Answer:
The phylum X is **Platyhelminthes**.