The main reason that it's important to test only one variable at a time is so that a. quantitative data can be recorded. b. qualitative data can be recorded. c. scientists can easily tell which variable caused the results. d. scientists can have many hypotheses tested at once.

What is the main difference between the central nervous system (cns) and the peripheral nervous system (pns)? .the cns involves the brain and spinal cord, and the pns involves the body nerves. the cns involves the body nerves, and the pns involves the brain and spinal cord. the cns involves sensory neurons, and the pns involves motor neurons. the cns involves motor neurons, and the pns involves sensory neurons.