Arthur reads an article describing an experiment to test the effects of caffeine on the reaction time of humans—how long it took them to respond to a particular signal. In the experiment, the subjects' reaction times were measured, then they were divided into three groups. One group was given a high dose of caffeine. The second group was given a medium dose of caffeine. The third group was given a sugar pill that had no caffeine. After waiting 45 min for the caffeine to take effect, the reaction times were measured again. In the experiment Arthur read about, what was the outcome variable (dependent variable)? A.
the amount of caffeine given to each person
B.
the change in reaction times for each person
C.
the type of signal each person responded to
D.
the amount of time the caffeine was given to take effect

Over the past 60 years, many amphibian species have experienced significant population declines and some species have become extinct. scientists suspected that local human activities such as the destruction of wetlands, regional pollution, and deforestation were the main reasons for these losses. however, research over the past 20 years reveals significant amphibian population declines in protected areas of the world, such as nature preserves and parks. these global declines suggest widespread problems including increased ultraviolet radiation, acid rain, and disease. in switzerland, for example, 14 of the 20 native amphibian species are threatened with extinction. chytridiomycosis is a fungal disease first identified in 1998 as a cause of massive amphibian deaths. in some severely impacted populations, a few individuals have survived, perhaps because of some natural resistance. if these resistant individuals continue to survive and prosper, new resistant populations might emerge. this would be an example of the founder effect artificial selection genetic drift natural selection sexual selection

If scientists are wrong about earth's age based on radioactive material and the decay rates are really much faster, how would nuclear power plants be affected?

Which statement describes john tuzo wilson’s contribution to the theory of plate tectonics?