How do scientists usually test for one variable

The indipendant variable  and the control and dependant variable

Explanation: Scientists identify what they want to test the independant variable and then they set up controls as a way of quality control and measure it which is the dependant variable hope this helps god bless

answer; /// i believe that the correct answer is (50%);

the atmospheric gas that forms a mild acid when dissolved in water is called carbon dioxide. the correct answer is a. 2.) chemical weathering would cause an inscription on a marble headstone to become harder and harder to read over time.