Which of the following is a microelement ?

Options

A. Chlorine
B. Hydrogen
C. Nitrogen
D. Oxygen

Answer

To solve the question "Which of the following is a microelement?", we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- Microelements (or micronutrients) are essential elements required by plants in very small quantities (less than 1 mg per gram of dry weight).
- Macroelements (or macronutrients) are required in larger quantities (from 1 mg to 1000 mg).

2. **Identify the Options**:
- The options given are: chlorine, hydrogen, nitrogen, and oxygen.

3. **Classify Each Element**:
- **Chlorine**: This is classified as a microelement.
- **Hydrogen**: This is a macroelement.
- **Nitrogen**: This is also a macroelement.
- **Oxygen**: This is generally classified as a macroelement.

4. **Determine the Correct Answer**:
- Among the options, the only microelement is **Chlorine**.

5. **Conclusion**:
- Therefore, the correct answer to the question is **Chlorine**.