—_______ Lin Tao and Zhang Yu present at the party? —Yes. They had a wonderful time yesterday afternoon. A. has been B. have been C. was D. were 答案:D船在静水中的航速是1 m/s,河岸笔直,河宽恒定,河水靠近岸边的流速为2 m/s,河中间的流速为3 m/s.。以下说法中正确的是( )A.因船速小于流速,船不能到达对岸B.船不能沿一直线过河C.船不能垂直河岸过河D.船过河的最短时间是一定的