Sarah performs an experiment to determine the effect of nitrogen on plants. she studies the effect of nitrogen on the growth of the root hair, height of the plants, and nodule formation. which factor is an independent variable? a) amount of nitrogen b) growth of root hair c) nodule formation d) height of the plants

The correct answer is option a) Amount of Nitrogen.

The variables are the factors, which can be changed in an experiment. The variables can be of two types, dependent variable and independent variable.

The independent variables are those factors, which are independent of any changes. In this case, the amount of nitrogen Sarah administer is not dependent on any factor, so, it is an independent variable.

Whereas, the height of plant, nodules and root growth is dependent on the amount of nitrogen the plant get. SO, these are dependent variables.