Number of C = O groups in thymine and in X are equal. Now, X is

Options

A. Cytosine
B. Uracil
C. Adenine
D. Guanine

Answer

To solve the question regarding the number of carbonyl (C=O) groups in thymine and the unknown compound X, we will analyze the structures of the nitrogenous bases mentioned in the options: cytosine, uracil, adenine, and guanine.

### Step-by-Step Solution:

1. **Identify the Structure of Thymine**:
- Thymine is a pyrimidine base with the chemical formula C5H6N2O2.
- In its structure, it contains two carbonyl (C=O) groups.

2. **Examine the Structures of the Other Bases**:
- **Cytosine**:
- Structure: C4H5N3O.
- Contains one carbonyl group and one amine group (NH2).
- **Uracil**:
- Structure: C4H4N2O2.
- Contains two carbonyl groups, similar to thymine.
- **Adenine**:
- Structure: C5H5N5.
- Contains no carbonyl groups; it has amine groups instead.
- **Guanine**:
- Structure: C5H5N5O.
- Contains one carbonyl group and one amine group.

3. **Compare the Number of Carbonyl Groups**:
- Thymine has 2 carbonyl groups.
- Uracil also has 2 carbonyl groups.
- Cytosine has 1 carbonyl group.
- Adenine has 0 carbonyl groups.
- Guanine has 1 carbonyl group.

4. **Conclusion**:
- Since the number of carbonyl groups in thymine and X are equal, and we found that uracil has the same number of carbonyl groups as thymine (2), we conclude that X is uracil.

### Final Answer:
X is uracil.