Which of the following is a pyrimidine base?

Options

A. Adenine
B. Guanine
C. uracil
D. None of these

Answer

To determine which of the following is a pyrimidine base, we first need to understand what a pyrimidine base is. Pyrimidines are a class of nitrogenous bases that have a single six-membered ring containing two nitrogen atoms. The most common pyrimidine bases found in nucleic acids are:

1. **Cytosine (C)**
2. **Thymine (T)**
3. **Uracil (U)**

Now, let’s analyze the options typically provided in such questions.

### Step-by-Step Solution:

1. **Identify the options given in the question.**
- For example, if the options are Adenine, Guanine, Cytosine, and Thymine, we need to evaluate each one.

2. **Recall the structure of pyrimidine bases.**
- Pyrimidine bases are characterized by their single-ring structure.

3. **Evaluate each option:**
- **Adenine (A)**: This is a purine base, which has a double-ring structure.
- **Guanine (G)**: This is also a purine base, with a double-ring structure.
- **Cytosine (C)**: This is a pyrimidine base, with a single-ring structure.
- **Thymine (T)**: This is also a pyrimidine base, with a single-ring structure.

4. **Select the correct answer(s).**
- From the analysis, both Cytosine and Thymine are pyrimidine bases.

### Conclusion:
The pyrimidine bases among the options provided are **Cytosine (C)** and **Thymine (T)**.