问题补充：
Some people waste too much water. They don’t believe that it can some day.
A. keep out
B. run out
C. be run out
D. run out of
答案：
A. keep out
(答案→)B. run out
C. be run out
D. run out of
解析：考查动词短语辨析。短语run out意为“用完，耗尽”，keep out“阻止……进入”，run out of “从……中跑出来；用完……东西”；选项C是被动形式，其后应加介词of。
