ACCORDING TO THE PASSAGE, A GREAT VARIETY OF INFLUENZA STRAINS CAN...

3. - 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

3. According to the passage, a great variety of influenza strains can appear when__________

A. H and N spikes are produced. B. Animal and bird viruses are combined.

C. Dissimilar types of virus recombine. D. Two viruses of the same type are contracted.