Sugars are attached to the pyrimidines by the formation of

Options

A. Hydrogen bond
B. N-glycosidic bond
C. Phosphoester bond
D. O-glycosidic bond

Answer

### Step-by-Step Solution:

1. **Identify the Components**: Understand that we are discussing the bond formed between sugars and pyrimidines. Pyrimidines include thymine, cytosine, and uracil.

2. **Recall the Types of Bonds**: The question provides four options for the type of bond:
- Hydrogen bond
- N-glycosidic bond
- Phosphoester bond
- O-glycosidic bond

3. **Understand the Structure**: In nucleic acids (DNA and RNA), the sugar (deoxyribose in DNA and ribose in RNA) is linked to the nitrogenous base (which can be a pyrimidine) at the first carbon of the sugar.

4. **Identify the Correct Bond**: The bond that links the sugar to the nitrogenous base (in this case, pyrimidine) is known as the **N-glycosidic bond**. This bond is formed between the nitrogen atom of the pyrimidine base and the first carbon atom of the sugar.

5. **Eliminate Incorrect Options**:
- **Hydrogen Bond**: This bond occurs between complementary bases (e.g., adenine and thymine) but not between sugar and base.
- **Phosphoester Bond**: This bond links nucleotides together in a nucleic acid strand, not between sugar and base.
- **O-glycosidic Bond**: This bond typically connects sugars to other molecules, not specifically between sugar and pyrimidine.

6. **Conclusion**: The correct answer is **N-glycosidic bond**, which is option 2.

### Final Answer:
The sugars are attached to pyrimidines by the formation of an **N-glycosidic bond**.

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