Concept:Land becomes a productive resource only when human effort is applied to it.
Explanation:Land is a free gift of nature, but by itself it cannot produce goods or services.
To make land useful, labour must be applied through activities such as clearing, tilling, and planting.
Fertilizer and machines can improve output, but they are not the primary means by which land becomes a factor of production.
Thus, the basic usefulness of land depends on the application of human effort.
Answer:A. application of human effort