Question

lets speed up the time while we expose the cells to the chemicals.
the exposure time was set to 48 hours.
what type of variable is the exposure time in this experiment?
a) independent variable
b) dependent variable
c) random variable
d) controlled variable

Explanation:

A controlled variable is a factor kept constant in an experiment to isolate the effect of the independent variable. Here, exposure time is set to a fixed 48 hours, so it is held consistent across the experiment.

Answer:

d) Controlled variable