To solve the question, we need to identify which group contains only micronutrients. Micronutrients are essential elements required by organisms in small quantities.
### Step-by-Step Solution:
1. **Understand Micronutrients**: Micronutrients are nutrients that are needed in smaller amounts compared to macronutrients. They include elements like zinc, copper, manganese, iron, etc.
2. **Analyze Each Option**:
- **Option A**: Sulfur, Molybdenum, Nitrogen
- Sulfur and Molybdenum are micronutrients, but Nitrogen is a macronutrient.
- **Option B**: Zinc, Copper, Manganese
- All three are known micronutrients.
- **Option C**: Oxygen, Iron, Potassium
- Iron is a micronutrient, but Oxygen is not a nutrient in the same sense, and Potassium is a macronutrient.
- **Option D**: Carbon, Chlorine, Nickel
- Carbon is a macronutrient, while Chlorine and Nickel are micronutrients.
3. **Identify the Correct Group**:
- From the analysis, only Option B (Zinc, Copper, Manganese) contains only micronutrients.
4. **Conclusion**: The correct answer is **Option B**.
