In an experiment, there are two groups. which group is not changed in any way?
a. control
b. experimental
c. variable
d. hypothesis

Correct A). Control

A control variable is something that is kept unchanged in the experiment. It is used as a standard of comparison that is used for checking the results of an experiment.

The control variable is not of primary concern in the experimental outcome. It increases the reliability of the results through a comparison between the control measurements and the other measurements.

Hence, the correct answer would be option A.

answer; i believe that the correct answer is(d) nondisjunction during meiosis;