Choanocytes are the characteristic cells of
A. Sycon
B. Euspongia
C. Pennatulla
D. Ctenoplana
E. Cliona

Options

A. A and B only
B. A, B and C only
C. A, B and D only
D. A, B and E only

Answer

To solve the question regarding which organism has choanocytes as characteristic cells, we can follow these steps:

### Step 1: Understand what choanocytes are
Choanocytes, also known as collar cells, are specialized cells found in sponges (phylum Porifera). They have a unique structure that includes a flagellum surrounded by a collar of microvilli, which helps in feeding and water circulation.

**Hint:** Remember that choanocytes are primarily associated with sponges.

### Step 2: Analyze the options provided
We have five options to consider:
- A. Sycon
- B. Euspongia
- C. Pennatula
- D. Ctenoplana
- E. Cliona

**Hint:** Look for organisms that belong to the phylum Porifera, as choanocytes are specific to this group.

### Step 3: Identify which options belong to phylum Porifera
- **Sycon**: This is a type of sponge and belongs to the phylum Porifera.
- **Euspongia**: This is also a sponge and belongs to the phylum Porifera.
- **Pennatula**: This is a type of soft coral and does not belong to the phylum Porifera.
- **Ctenoplana**: This is a type of ctenophore (comb jelly) and does not belong to the phylum Porifera.
- **Cliona**: This is a genus of boring sponges, which also belong to the phylum Porifera.

**Hint:** Focus on identifying sponges among the options.

### Step 4: Determine which sponge is most characteristic of choanocytes
Both Sycon and Euspongia are sponges and contain choanocytes. However, Euspongia is well-known for its commercial use and is often referred to as "bath sponge," which is a common example of sponges that have choanocytes.

**Hint:** Consider which sponge is most commonly associated with choanocytes in educational contexts.

### Step 5: Choose the correct answer
Given the analysis, the correct answer is **B. Euspongia**, as it is a sponge that is well-known for having choanocytes as its characteristic cells.

**Final Answer:** B. Euspongia