TOEFL Listening: ETS-TOEFL听力机经 - IYP413GA43N3G21FP$

How did Derryberry's research with female white-crested sparrows differ from her research with male white-crested sparrows? A. Only the female birds were in cages. B. More female birds than male birds were studied. C. Mating songs were only played to female birds. D. Male birds were studied for a longer time than female birds were.