TOEFL Listening: TPO-TOEFL听力TPO - _63697ETZ1WN7064R$

What does the professor say people have done to help hummingbirds survive? A. They have built a series of hummingbird feeding stations B. They have supported new laws that punish polluters of wildlife habitats C. They have replanted native flowers in once polluted areas D. They have learned to identify various hummingbird species