Vitamin `B_(1)` is:

Options

A. Riboflavin
B. Cobalalmin
C. Thiamine
D. Pyridoxine

Answer

To solve the question "Vitamin B1 is:", we will analyze the options provided and identify which one corresponds to Vitamin B1.

### Step-by-Step Solution:

1. **Identify the Options**:
- Option 1: Riboflavin
- Option 2: Cobalamin
- Option 3: Thymine
- Option 4: Pyridoxin

2. **Recall the Names of Vitamins**:
- Vitamin B1 is known for its role in metabolism and nerve function.
- Riboflavin is actually Vitamin B2.
- Cobalamin is known as Vitamin B12.
- Pyridoxin is Vitamin B6.

3. **Determine the Correct Answer**:
- The only option left is Thymine, which is also known as Thiamine.
- Thiamine is indeed recognized as Vitamin B1.

4. **Conclusion**:
- Therefore, the correct answer is Option 3: Thymine.

### Final Answer:
Vitamin B1 is Thymine (Option 3).