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.

answer; (consensus);

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