The nitrogenous bases of the two strands of DNA are joined by

Options

A. Phosphodiester bond
B. Hrdrogen bond
C. Glycosidic bond
D. Peptide bond

Answer

### Step-by-Step Solution:

1. **Understanding DNA Structure**: DNA (deoxyribonucleic acid) is the genetic material that carries information from one generation to the next. It has a double helical structure proposed by Watson and Crick.

2. **Identifying the Components**: DNA consists of two strands that are twisted around each other. The strands are made up of nucleotides, which include a sugar, a phosphate group, and a nitrogenous base.

3. **Nitrogenous Bases**: The nitrogenous bases in DNA are categorized into two types:
- **Purines**: Adenine (A) and Guanine (G).
- **Pyrimidines**: Thymine (T) and Cytosine (C).

4. **Base Pairing**: In the double helix, the nitrogenous bases from one strand pair with those from the other strand:
- Adenine pairs with Thymine (A-T) via **two hydrogen bonds**.
- Cytosine pairs with Guanine (C-G) via **three hydrogen bonds**.

5. **Joining of Strands**: The nitrogenous bases of the two strands of DNA are joined together by **hydrogen bonds**. These bonds are crucial for maintaining the structure of DNA and allowing it to function properly.

6. **Conclusion**: Therefore, the nitrogenous bases of the two strands of DNA are joined by **hydrogen bonds**.

### Final Answer:
The nitrogenous bases of the two strands of DNA are joined by **hydrogen bonds**.

---