An Experiment Is a Study in Which a Researcher

An experiment is a study in which a researcher:

A) records dependent measures among members of naturally occurring groups (e.g. ,gender) and looks for systematic differences.
B) observes the development of one or more variables in a group of individuals over time at regular intervals.
C) measures the degree and direction of association between two variables.
D) takes active control of an independent variable,manipulates it,and observes its effect on a dependent variable.