A) The independent variable* is the factor that is intentionally changed or manipulated by the experimenter.

Here are the variables for Rama's experiment:

*a) The independent variable is the factor that is intentionally changed or manipulated by the experimenter.
In this experiment, Rama is changing the fertilizer to observe its effect.
The independent variable is the amount or type of fertilizer.

*b) The controlled variables are the factors that are kept constant throughout the experiment to ensure that only the independent variable is affecting the dependent variable.
Examples of controlled variables include the type of plant, amount of water, amount of sunlight, type of soil, and temperature.

*c) The dependent variable is the factor that is measured or observed and is expected to change in response to the independent variable.
In this experiment, Rama is measuring the effect on plant growth.
The dependent variable is the plant growth.