阿摩線上測驗
12. Once an outbreak of a deadly virus occurs, public health workers ______ its spread.
(A) track
(B) tracking
(C) are track of
(D) who track
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統計： A(470), B(325), C(287), D(110), E(0) #2350344
統計： A(470), B(325), C(287), D(110), E(0) #2350344
