To provide a baseline against which they can evaluate the effects of a specific treatment, experimenters make use of a(n)
a.
dependent variable.
b.
random sample.
c.
independent variable.
d.
control condition.
e.
experimental condition.

d.  control condition

Explanation:

When carrying out an experiment, a control condition is set up to provide a baseline against which the result of the experiment can be compared. For example, when measuring the effects of a new medication, a control group is usually set up and the members of the group are given a placebo. This will not contain any of the active ingredients of the medicine and it acts as a way to evaluate the real effects of the medication.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.