Which of the following are testable hypotheses that could explain the researchers' data?

Select all that apply.

A. Scavenger population sizes have increased, and more road-killed swallows get eaten before they can be found.
B. The number of cars driving on these roads has increased over time.
C. The population size of cliff swallows living near roads has decreased over time.
D. Traits that help individuals avoid being hit by cars have evolved through natural selection in the cliff swallow population.
E. An unknown element has been protecting the swallows.