一般是凭（）来检测电解铝的质量。
A.米尺
B.经验
C.天平
参考答案：B
Unfortunately, when I dropped in, Doctor Li _____ for Beijing to join in the fight again H1N1, so we only had time for a few words.
A．just left
B．has just left
C．is just leaving
D．was just leaving
When a person wants to operate the computer, _____ read instructions first.
A．you will have to
B．one must
C．they will have to
D．he has to
