Which of the following is an example of a macronutrient?

Macronutrients are substances that organisms need in larger amounts for normal growth and development. They are the fundamental building blocks required for essential functions including growth, metabolism, and cellular structure. Nitrogen is classified as a macronutrient because it is a critical component of amino acids, proteins, and nucleic acids, all of which are vital for life. In plants, nitrogen plays a key role in their ability to synthesize chlorophyll, which is essential for photosynthesis.

The other options—iron, copper, and zinc—are classified as micronutrients. While they are essential for organisms, they are required in much smaller quantities compared to macronutrients. Iron, for instance, is important for oxygen transport in blood (hemoglobin), copper plays various roles in enzyme functions, and zinc is crucial for immune function and enzyme activity. Understanding the distinction between macronutrients and micronutrients is key in fields like ecology, agriculture, and nutrition.