It allows the scientist to determine the effect of the changed variable , it also allows samples and organisms to be tested under comfortable conditions
Answer: The correct answer is: It allows the scientist to determine the effect of the changed variable.
Explanation: It ensures the reproduciblity of that experiment and hence, it increases the reliability of that experiment.
For example, if scientist is checking the effects of temperature on enzyme activity then other factors such as amount of enzyme, substrate, pH, pressure etc should be controlled as they can alter the results.
