柱塞式喷油泵由泵体、泵油机构、传动机构和（）四大部分组成。
A.柱塞副
B.油量控制机构
C.输油泵
参考答案：B
Her friend did everything in his ________ to help with her business.
A．energy
B．power
C．strength
D．force
尝试一错误学说的学习定律包括( )．
A．效果律
B．学习律
C．练习律
D．准备律
