TOEFL Listening: ETS-TOEFL听力机经 - V1XP35459ONRBCVAP$

The professor explains the method the researchers in Hungary used in their study. Which of the following are problems that she says the researchers were aiming to avoid? A. Disturbing the mammals whose fur they were collecting. B. Making nests unsuitable for future use by birds. C. Leaving human footprints in forested areas. D. Interfering with birds' raising of their young.