Which of the following could negatively affect the reliability of an experiment? A.testing only one variable at a time
B.having variables that are difficult or even impossible to control
C. keeping the control monitored to make sure it remains unchanged
The answer to this is B. When conducting an experiment, you should only manipulate one variable at a time and all other variables should be kept as similar as possible in order to ensure that the results are caused by one thing and not another.
