Which one of the following is a micro-element ? A. Chlorine B. Hydrogen C. Nitrogen D. Oxygen

Hydrogen, nitrogen, and oxygen are macronutrients, which means that they are required by plants in large amounts. Hydrogen is a component of water, which is essential for all life. Nitrogen is a component of proteins, nucleic acids, and other essential molecules. Oxygen is a component of air, which is necessary for respiration.

In conclusion, chlorine is a micro-element because it is required by plants in very small amounts. It is essential for the formation of chlorophyll, which is necessary for photosynthesis. Chlorine also helps to regulate the plant’s water balance and to protect it from pests and diseases.