Which of the following compounds is used in the preservation of biological specimens?

Options

A. `CH_(3)CHO`
B. `CH_(3)COOH`
C. `CH_(3)-O-CH_(3)`
D. `HCHO`

Answer

To determine which compound is used in the preservation of biological specimens, we can analyze the options provided in the question.

### Step 1: Identify the compounds listed
The compounds mentioned in the question are:
1. CH3CHO (Acetaldehyde)
2. CH3COOH (Acetic acid)
3. CH3OCH3 (Dimethyl ether)
4. HCHO (Formaldehyde)

### Step 2: Understand the role of preservatives
Preservatives are substances used to prevent decay or spoilage of biological specimens. They help in maintaining the integrity of the specimens for study or storage.

### Step 3: Analyze each compound
- **Acetaldehyde (CH3CHO)**: While it is an aldehyde, it is not commonly used for preservation.
- **Acetic acid (CH3COOH)**: This is a weak acid and is not primarily used for the preservation of biological specimens.
- **Dimethyl ether (CH3OCH3)**: This compound is an ether and does not serve as a preservative.
- **Formaldehyde (HCHO)**: This is a well-known preservative. It is commonly used in a diluted form known as formalin, which is 30-40% formaldehyde in water. Formaldehyde is effective in preserving biological specimens by hardening tissues.

### Step 4: Conclusion
Based on the analysis, the correct compound used for the preservation of biological specimens is **Formaldehyde (HCHO)**. Therefore, the correct option is **option D**.

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