In conducting their research, economists often substitute historical events and historical episodes for

a. theories and observations.

b. laboratory experiments.

c. models.

d. assumptions.

b. laboratory experiments.

Explanation:

Laboratory experiments -

It refers to the practice of an experiment in a appropriate and controlled condition, is referred to as the laboratory experiments.

In this case, the experiment involve some standard conditions, which are necessary for the experiment to occur.

Hence, from the given information of the question,

The correct option is laboratory experiments.