护理论文的核心部分是
A．前言
B．材料和方法
C．结果
D．讨论与分析
E．参考文献
参考答案：C
— Sixteen –year-olds should ____ to drive.
A．not be allowed
B．be allowed
C．not be allowed
D．be allow
We have math ________ Friday. It's difficult ________ interesting.[ ]
A. on, or
B. on, and
C. in, or
D. in, and
