Answer:
a. cause ; effect
Step-by-step explanation:
A variable is any factor that can sustain in varying types or amounts.
There are actually three types of variables: dependent variable, independent variable and controlled variable.
The controlled variable is that trait or condition the experimenter desires to keep constant.
The dependent variable is contingent upon the independent variable. It is determined by the independent variable. The effects of the actions taken on the independent variables are seen on the dependent variables. These two variables are related by cause and effect.