ACCORDING TO THE PASSAGE, SCIENTISTS HAVE DISCOVERED THAT INFLUENZA...

1. - 2 DE THI THU DH MON THI TIENG ANH VA DAP AN
Tiếng Anh 2 DE THI THU DH MON THI TIENG ANH VA DAP AN

1. According to the passage, scientists have discovered that influenza viruses __________

A. cause ill health in wild animals. B. do not always cause symptoms in birds.

C. are rarely present in wild birds. D. change when transmitted from animals to man.