Question

In his experiment on spontaneous generation, Louis Pasteur changed only one thing between his experimental groups: whether or not the neck of the flask was broken. That means that his experiment was _____.

Answer 1

Louis Pasteur's experiment was A) controlled.

A scientist must change only one variable at a time to see if it is the one causing the observed change.

The scientist must keep all the other variables constant (i.e. control the variables)