To determine which elements are critical for plant growth, we will analyze the given options step by step.
### Step-by-Step Solution:
1. **Understanding Critical Elements**:
- Critical elements for plant growth refer to essential nutrients that plants require in significant amounts for their development and physiological processes.
2. **Analyzing the Given Options**:
- The options provided are:
- Option 1: Carbon, Hydrogen, Oxygen
- Option 2: Calcium, Magnesium, Sulphur
- Option 3: Nitrogen, Phosphorus, Potassium
- Option 4: Manganese, Iron, Copper
3. **Evaluating Option 1 (Carbon, Hydrogen, Oxygen)**:
- Carbon: Forms the backbone of organic molecules and is essential for the production of proteins, starch, and cellulose.
- Hydrogen: Plays a role in the electron transport system during photosynthesis.
- Oxygen: Involved in cellular respiration.
- **Conclusion**: While these elements are vital for life processes, they are not classified as critical nutrients for growth directly.
4. **Evaluating Option 2 (Calcium, Magnesium, Sulphur)**:
- Calcium: Important for cell wall formation but does not directly promote growth.
- Magnesium: A component of chlorophyll, essential for photosynthesis.
- Sulphur: Necessary for the formation of proteins, enzymes, vitamins, and chlorophyll.
- **Conclusion**: While these elements are important, they are not the primary nutrients that directly promote growth.
5. **Evaluating Option 3 (Nitrogen, Phosphorus, Potassium)**:
- Nitrogen: A major component of chlorophyll; essential for photosynthesis and overall plant growth.
- Phosphorus: Crucial for the formation of DNA and RNA, important for energy transfer (ATP).
- Potassium: Regulates photosynthesis and is involved in various physiological processes.
- **Conclusion**: These three elements are critical for plant growth and development.
6. **Evaluating Option 4 (Manganese, Iron, Copper)**:
- Manganese: A micronutrient involved in various enzymatic processes.
- Iron: Important for chlorophyll synthesis and electron transport.
- Copper: Plays a role in lignin synthesis.
- **Conclusion**: These are micronutrients and, while necessary, they do not play a major role in direct growth promotion.
7. **Final Decision**:
- Based on the evaluations, **Option 3 (Nitrogen, Phosphorus, Potassium)** is the correct answer as these elements are critical for plant growth.
