In medical experiments, which group receives placebos?
the experimental group
the control group
both the experimental and control groups
neither the experimental nor control group

All of the following are part of the biosphere except

What is the independent variable in this investigation? mass volume sample number substance density

How are evaporation and sublimation similar? a both involve the formation of a gas. b both release energy to the surroundings. c both take place throughout a solid. d both take place at the surface of a liquid.