When pathogenic bacteria lose the ability to make adhesins owing to insertion of Tn5 into the gene of pili, they typically ________________.
A. become avirulent
B. produce modified enzyme to break kanamycine
C. Produce endotoxin
D. decrease in virulence
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Which statement about normal flora are right __________.
A. Inhibit R plasmid spread among different bacteria species.
B. Activate immune cells;
C. Antagonism against foreign bacteria;
D. Provide Vit.K to the host;
Directions: There are 10 incomplete sentences in this part. For each sentence there are 4 choices marked A, B, C and D. Choose the answer that best completes the sentence.1. She held her hands above her eyes to ______them ______ the sun so that she could see more clearly the man in front of her.
A. count … on
B. make sense … of
C. reserve … for
D. shield … from
2.The boy studied the signs for over an hour, but still could not __________ them, so he turned to his teacher for help.
A. count on
B. make sense of
C. reserve for
D. shield from
3.They __________ the developed countries to commit more money to protecting the environment.
A. called on
B. sumed up
C. in need
D. shielded from