非处理因素应尽量保持一致，符合( )
A．对照的原则B．重复的原则C．随机化原则D．节约化原则E．最优化原则
参考答案：C
_______no doubt that a green campus plays an important role in the growth of students, both physically and mentally.
A．It is
B．There has
C．There is
D．It has
按风险的来源，投资风险可分为( )。
A．纯粹风险和投机风险
B．静态风险和动态风险
C．基本风险和特定风险
D．系统风险和非系统风险
