题干
–What’s the noise?
–It’s the drill. Since the beginning of the term, the workers _______ our heating system.
A：are repairing
B：have been repairing
C：will be repairing
D：repair
答案(点此获取答案解析）
B
km/h的静水速度按垂直于对岸的方向行驶，同时河水的流速为10km/h．则小船实际航行速度的大小为（ ）