时间定额与产量定额之间的关系是（）。
A.两者之和为零
B.两者相等
C.两者互为倒数
D.两者之差为小组成员工日数总和
参考答案：C
简述羊水栓塞的处理原则。
English teaching in China didn't enter into the formal educational system until the ______ century.
A. late 19th B. early 20thC. mid-20th D. late 20th
