问题
选择题
—What a nice bike! How long ____ you ____ it?
—Just two weeks.[ ]
A. have; bought
B. did; buy
C. have; had
D. are; having
答案
答案：C
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—What a nice bike! How long ____ you ____ it?
—Just two weeks.[ ]
A. have; bought
B. did; buy
C. have; had
D. are; having
答案：C
某人划船过一条河，当划行速度和水流速度一定，且划行速度大于水流速度时，过河的最短时间是t1，若以最小位移过河，需要时间t2，则划行速度v1和水流速度v2之比为（ ）
| A．t2：t1 | B．t2：
| C．t1：（t1-t2） | D．
|