20.修一条公路,甲队单独修15天完成,乙队单独修12天完成,甲队工作效率比乙队慢了( )
| A. | 25% | B. | 20% | C. | 33.3% | D. | 26.7% |
19.一场体育比赛中,共有12名运动员.如果每两个人握一次手共握( )手.
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| A. | 28 | B. | 56 | C. | 66 | D. | 24 |