Which is not a mutagen?

Options

A. (a) acetic acid
B. (b) gamma rays
C. (c) nitrous acid
D. (d) hydroxylamine

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which option is not a mutagen. A mutagen is an agent that causes changes (mutations) in the genetic material (DNA).

2. **Types of Mutagens**: There are three main types of mutagens:
- **Physical Mutagens**: These include radiation such as gamma rays, which can cause irreversible changes in DNA.
- **Chemical Mutagens**: These are chemical agents that can alter DNA, such as nitrous acid and hydroxylamine.
- **Biological Mutagens**: These include certain viruses and bacteria that can induce mutations.

3. **Analyzing the Options**: The options provided need to be evaluated to determine which one does not fit the definition of a mutagen.
- **Option A: Acetic Acid**: This is a chemical compound commonly used in laboratories. While it can cause irritation, it does not cause irreversible or inheritable changes in DNA, thus it is not considered a mutagen.
- **Option B: Gamma Rays**: These are a type of physical mutagen that can cause significant damage to DNA.
- **Option C: Nitrous Acid**: This is a chemical mutagen that can lead to changes in DNA structure.
- **Option D: Hydroxylamine**: This is also a chemical mutagen known to cause mutations.

4. **Conclusion**: Since acetic acid does not cause irreversible or inheritable changes in DNA, it is identified as the option that is not a mutagen. Therefore, the correct answer is **Option A: Acetic Acid**.