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The flu is believed _________ by viruses that like to reproduce in the cells inside the human nose and throat.                                                 

 A. causing        B. being caused      C. to be caused       D. be have caused

The flu is believed______by viruses that like to reproduce in the cells inside the human nose and throat.

A.causing                            B.being caused

C.to be caused                      D.to have caused

The flu is believed _______ by viruses that like to reproduce in the cells inside the human? nose and throat.?

A. causing B. being caused?

C. to be caused D. be have caused?

The flu is believed ______ by viruses that like to reproduce in the cells inside the human nose and throat.

A. to be caused                   B. to have caused               C. being caused                   D. causing

The flu is believed ______ by viruses that like to reproduce in the cells inside the human nose and throat.

A. to be caused                   B. to have caused               C. being caused                   D. causing

The flu is believed ____by viruses that like to reproduce in the cells inside the human nose and throat.

    A. causing   B. being caused   C. to be caused   D. to have caused

The flu is believed____ by viruses that like to reproduce in the cells inside the human nose and throat.

A. causing      B. being caused      C.  to have caused       D. to be caused

The flu is believed__________by viruses that like to reproduce in the cells inside the human nose and throat.?

A.causing?

B.being caused?

C.to be caused?

D.be have caused?

The flu is believed _____ by viruses that like to be reproduced in the cells inside the human nose and throat.

A. causing　　　　　　 B. being caused

C. to be caused　　　　 D. to have caused