Which of the following elements is required in gram quantities?

The answer is calcium, which is required in gram quantities because it plays vital roles in various biological functions. Calcium is a major component of bones and teeth and is essential for maintaining structural integrity. Additionally, it is crucial for muscle contraction, nerve transmission, and blood clotting. The human body requires a relatively high amount of calcium daily—typically 1,000 to 1,200 mg per day for adults to support these essential physiological processes.

In contrast, elements such as iron, potassium, and copper are trace elements that the body needs in much smaller quantities, often measured in milligrams or micrograms. While they are important for various functions—like oxygen transport for iron, cellular function for potassium, and enzyme activity for copper—they do not reach the requirement levels seen with calcium.