Just because one hypothesis may help to explain a phenomenon does not mean it is the only hypothesis that could explain it. Imagine you are a scientist investigating why frog populations are declining in a state county with several hundred ponds.
There could be multiple reasons why frog populations are declining in the county, and therefore, it would be wise to test multiple hypotheses. Some experiments may be observational, in which the researcher observes and measures naturally occurring variations in the dependent variable. Other experiments may be manipulative, in which the researcher directly manipulates the independent variable to test the effect on the dependent variable being measured.
Match the experiments to the hypotheses they test. Make sure to distinguish between the observational experiments and the manipulative experiments.