This passage supports the belief that ______.
A: exact reasons for migration are not known
B: glaciers caused birds to migrate
C: the ancestral home of birds was the tropics
D: birds migrate because of changes in temperature
A: exact reasons for migration are not known
B: glaciers caused birds to migrate
C: the ancestral home of birds was the tropics
D: birds migrate because of changes in temperature
举一反三
- It's strange that birds know when to ___________ and find their way back home. A: immigrate B: migrate C: emigrate D: immigrant
- 【单选题】Which of the following is the best title for this passage? A. The Best Way to Keep Birds B. A Story of A Girl and Two Birds C. To Love Birds Is to Give Them Freedom D. Give Love Wings
- According to the passage, scientists have discovered that influenza viruses ______ . A: cause ill health in wild birds B: do not always cause symptoms in birds C: are rarely present in wild birds D: change when transferred from animals to man
- It must be morning, ____ the birds are singing. A: for B: because C: as D: since
- In Chapter IV, the author would like to give you information about ______. A: how to attract birds B: seasonal flights of birds C: language of birds