TOEFL Reading: ETS-TOEFL阅读机经 - PKZFS7S7V016DY76L$

According to paragraph 2, Ryan and Rand conducted an experiment to find out whether which of the following theories was true A. Male frogs in a chorus use a whine-chuck call in place of a whine call. B. Female frogs prefer a whine-chuck call to a simple whine call. C. Male frogs tend to produce more whine-chuck calls than whine calls. D. Female frogs respond differently to live calls from males than they do to recorded calls.