The element which is required in the largest quantity by plants is

1. sulphur
2. calcium
3. phosphorus
4. nitrogen

Correct Answer: (d) nitrogen

Explanation:

 Nitrogen is required in the largest quantity by the plants.

Plants need nitrogen because it is the major component of amino acids. Nitrogen is also a building block of protein. 

Plants obtain nitrogen from the soil by inorganic salts like nitrites or nitrates in the form of organic compounds produced by bacteria using atmospheric nitrogen.

Plants also obtain nitrogen from the NPK (Nitrogen, phosphorus, and potassium) fertilizers.

Plants need nitrogen as a fundamental component of chlorophyll, which they need to make carbohydrates from water and carbon dioxide (i.e., photosynthesis).

Plants perish without proteins. Some proteins are structural components in plant cells, while others are enzymes that enable biochemical processes essential to life.

Nitrogen is a component of ATP (adenosine triphosphate). ATP stores and uses metabolic energy.

Nitrogen is a key component of nucleic acids like DNA, which allow cells (and eventually plants) to develop and reproduce. Without nitrogen, life wouldn't exist.