The element required in maximum quantity by plants is
A. Sulphur
B. Iron
C. Phosphorus
D. Nitrogen

Hint: Elements that are required in more quantities by the plants are known as macronutrients while those required in lesser amounts are known as micronutrients.

Complete answer: Plants require many nutrients to control their growth and development.
The nutrients which are required by the plants in larger quantities are known as macronutrients and those which are required by the plants in small or lesser amounts are known as the micronutrients.
Elements like copper, iron, boron, zinc, molybdenum, and chloride are micronutrients. While nutrients like nitrogen, carbon, hydrogen, oxygen, and sulfur, etc are macronutrients.
Out of the three macronutrients listed in the question, the one which is required in the maximum quantity that is around 1.5% is nitrogen.

Additional information: Nitrogen is a very major and needed for plant growth.
It is found in soils, and provide plants the energy to grow, and produce fruit or vegetables. Nitrogen is a component of the chlorophyll molecule, which gives plants their characteristic green color and is involved in producing food for the plant through photosynthesis.

Hence, the correct option is (D), Nitrogen.

Note: Macronutrients are required in larger quantities, still, the presence of micronutrients is equally important for the plant to grow and complete various metabolic processes.