建筑物起火后多少分钟内是灭火的最好时间。
参考答案：
5-7分钟。
A good friend of mine from ________ I was born showed up at my home right before I left for Beijing.[ ]
A. how
B. whom
C. when
D. which
— I haven't seen Tom these days. Where is he?
— He _____ Japan.[ ]
A. has been to
B. has gone to
C. has been in
D. went to
