Which of these statements about centrioles is correct ?

Options

A. There are two centrioles in animal cells which lie perpendicular to each other within a centromere.
B. They have nine doublets of radially arranged peripheral fibrils.
C. The central part of the distal region of the centriole is proteinaceous and is called the hub.
D. The centrioles form the basal body of cilia of flagella, and spindle fibers that give rise to spindle apparatus during cell division in animal cells.

Answer

To determine which statement about centrioles is correct, let's analyze the provided statements step-by-step.

### Step 1: Understanding the Structure of Centrioles
- Centrioles are cylindrical structures found in animal cells, typically occurring in pairs.
- They are composed of microtubules arranged in a specific pattern.

**Hint:** Remember that centrioles are usually found in pairs and have a specific arrangement of microtubules.

### Step 2: Analyzing the First Statement
- The first statement claims that there are two centrioles in animal cells which lie perpendicular to each other.
- This statement is correct; centrioles are indeed found in pairs and are oriented at right angles to one another.

**Hint:** Think about the orientation of centrioles in relation to each other.

### Step 3: Analyzing the Second Statement
- The second statement mentions that there are nine doublets of radially arranged peripheral fibers.
- However, this is incorrect. Centrioles actually have nine triplets of microtubules arranged in a circular pattern, not doublets.

**Hint:** Focus on the arrangement of microtubules in centrioles.

### Step 4: Analyzing the Third Statement
- The third statement refers to the central part of the distal region of the centriole as proteinaceous and called the hub.
- This is misleading; the hub is located at the center of the centriole, not specifically in the distal region.

**Hint:** Clarify the location of the hub within the structure of the centriole.

### Step 5: Analyzing the Fourth Statement
- The fourth statement claims that the centriole forms the basal body of cilia or flagella and spindle fibers during cell division.
- This statement is correct. Centrioles play a crucial role in the formation of cilia and flagella and are essential for the organization of the spindle apparatus during cell division.

**Hint:** Consider the functions of centrioles in cell division and motility.

### Conclusion
After analyzing all the statements:
- The correct statement about centrioles is the first and the fourth statements. However, since the question asks for the correct statement, the fourth statement is the most comprehensive and accurate regarding the function of centrioles.

**Final Answer:** The correct statement is that centrioles form the basal body of cilia or flagella and spindle fibers during cell division in animal cells.