题目

He never thought of it before, ________all that his parents had done for him for granted.         A.taking  B.taken   C.to take D.took 答案：A有一小船正在渡河，如图所示，在离对岸30 ｍ时，其下游40ｍ处有一危险水域.假若水流速度为5 m/s，为了使小船在危险水域之前到达对岸，那么，小船从现在起相对于静水的最小速度应是     m/s.