The robber was caught by two men police uniform .A. in; at the onceB. in; at onceC. on,;

The robber was caught by two men police uniform .
A. in; at the once
B. in; at once
C. on,; at the once
D. on; at once

A. in; at the once(答案→)B. in; at onceC. on,; at the onceD. on; at once解析：in在里面;on在上面;句意:劫匪立即被两个身穿警服的男人抓住了.介词in可以表示穿某种衣服,短语at once立即,不要冠词,故选B.

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