“为搞好安全生产特制订计划”是一则计划的开头。这种开头属于（）
A、根据式
B、目的式
C、情况式
D、由总结前段情况引入式
参考答案：B
The number ofstudents in our school ____ about 2.000 and ____ them work hard at their lessons. [ ]
A. is; a large amount of
B.are; a number of
C. is; a good many
D. is; a large number of
简述人群出生缺陷监测的对象及监测期限。
