The part of a DNA molecule that varies among DNA molecules is its :

Options

A. glycerol attachments
B. nitrogenous bases
C. sugars
D. phosphates

Explanation

To solve the question, "The part of a DNA molecule that varies among DNA molecules is its:", we can analyze the options provided and understand the structure of DNA.

### Step-by-Step Solution:

1. **Understanding DNA Structure**:
- DNA (Deoxyribonucleic Acid) is a long polymer made up of repeating units called nucleotides. Each nucleotide consists of three components: a phosphate group, a sugar (deoxyribose), and a nitrogenous base.

2. **Identifying the Components**:
- The three main components of DNA are:
- **Phosphate Group**: This part is consistent across all DNA molecules.
- **Sugar**: In DNA, the sugar is always deoxyribose, which is also consistent.
- **Nitrogenous Bases**: These are the variable components and include adenine (A), thymine (T), cytosine (C), and guanine (G).

3. **Analyzing the Options**:
- **Option A: Glycerol attachments**: This is incorrect as glycerol is not a component of DNA; it is found in lipids.
- **Option B: Nitrogenous bases**: This is correct because the sequence and type of nitrogenous bases can vary among different DNA molecules, leading to genetic diversity.
- **Option C: Sugars**: This is incorrect as all DNA molecules contain the same sugar, deoxyribose.
- **Option D: Phosphates**: This is incorrect since the phosphate group is the same in all DNA molecules.

4. **Conclusion**:
- The part of a DNA molecule that varies among DNA molecules is the **nitrogenous bases**. Therefore, the correct answer is **Option B: Nitrogenous bases**.

### Final Answer:
The part of a DNA molecule that varies among DNA molecules is its **nitrogenous bases**.