常用的水井钻机有几类？
参考答案：
有四类，冲击钻机、回转钻机、冲击回转钻机、半机械化钻机。
It is ______ to spend money in preventing illnesses by promoting healthy living rather than spending it trying to make people ______ after they are ill.
A．good; good
B．well; better
C．better; better
D．better; good
碎（砂）石桩的承载力主要决定于：
A．桩身强度
B．桩端土的承载力
C．桩间土的约束力
D．砂石的粒径
