Answer:
A). An independent variable
Step-by-step explanation:
The Independent variable is characterized itself as the variable that is controlled or manipulated by the experimenter to observe its direct impact on the dependent variable. It is a variable that is not dependent and can stand alone. For example, if a student aims to observe the impact of temperature on solubility of a substance(sugar/salt) in a liquid, the temperature will be the independent variable as any change in the temperature will directly affect the solubility power of the liquid. Thus, option A is the correct answer.