Vitamin `B_(2)` is :

Options

A. thiamine
B. pantothenic acid
C. pyridoxine
D. retinol.

Explanation

To solve the question "Vitamin B2 is:", we will analyze the options provided and identify the correct answer step by step.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- Option 1: Thiamine
- Option 2: Pantothenic acid
- Option 3: Pyridoxine
- Option 4: Retinol

2. **Recall the Definition of Vitamin B2**: Vitamin B2 is known as riboflavin. It is a water-soluble vitamin that plays a crucial role in energy production and the metabolism of fats, drugs, and steroids.

3. **Analyze Each Option**:
- **Option 1: Thiamine** - This is actually Vitamin B1, not B2. Therefore, this option is incorrect.
- **Option 2: Pantothenic acid** - This is Vitamin B5, which is also not related to Vitamin B2. Hence, this option is incorrect.
- **Option 3: Pyridoxine** - This is Vitamin B6, which again does not correspond to Vitamin B2. Thus, this option is incorrect.
- **Option 4: Retinol** - This is Vitamin A, which is not related to Vitamin B2. Therefore, this option is incorrect.

4. **Conclusion**: After analyzing all the options, it is clear that none of the options correctly represent Vitamin B2 (riboflavin). However, the correct answer should be riboflavin, which is not listed among the options provided.

### Final Answer:
None of the options correctly describe Vitamin B2 (riboflavin).