简答什么叫楼地面。
参考答案：
楼地面是对楼层地面和底层地面的总称。
As we know, penicillin became the greatest drug of the 20th century, ______ millions of lives.
A．to save
B．saving
C．saved
D．Save
-- I heard a student killed his mother cruelly.
-- So did I. It has ____ a serious problem about the education system in China.
A．taken up
B．made up
C．pulled up
D．brought up
