当柱为预制时，则将基础做成杯口形，然后将柱子插入，并嵌固在杯口内，称为（）
A.刚性基础
B.柔性基础
C.杯口基础
D.条形基础
参考答案：C
Years ago we didn’t know this , but recent science______that people who don’t sleep well soon get ill.
A．showed
B．has shown
C．will show
D．is showing
