21.   While confirmatory tests are pending, the FDA closed all mailrooms for cleaning and put its workers on preventive antibiotics.

a. + antibiotic >>共 171
new 8.03%
intravenous 7.65%
common 4.40%
preventive 4.02%
oral 3.63%
powerful 3.44%
different 2.87%
potent 2.29%
broad-spectrum 2.10%
natural 1.91%
preventive + n. >>共 117
measure 28.85%
care 8.33%
medicine 7.40%
security 6.46%
diplomacy 3.54%
treatment 3.44%
service 3.23%
maintenance 3.23%
action 2.81%
health 2.29%
antibiotic 2.19%
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