6. Bird flu, a viral disease of birds, does not usually ______ humans; however,
some viruses, such as H5N1 and H7N9, have caused serious diseases in people.
(A) infect (B) inform (C) illustrate (D) inflate
13. A research result shows that drinking a lot of water can help_the
risk of developing kidney stones.
(A) inflate (B) promote (C) maximize (D) decrease