—How was your weekend?

—We ______ great fun playing in the park. 　 [ ]

A. have

B. were

C. had

D. has

一个水池装一个进水管和三个同样的出水管。先打开进水管，等水池存一些水后，再打开出水管（进水管不关闭）。若同时打开2个出水管，那么8分钟后水池空；如果同时打开3个出水管，则5分钟后水池空，那么出水管比进水管晚开（    ）分钟。