临产的主要标志是
A.不规则宫缩
B.见红
C.规律性宫缩, * * 流血
D.规律性宫缩,宫颈口扩张
E.规律性宫缩并逐渐加强,伴宫颈口扩张和胎先露下降
参考答案:E
两半径为a和b(a0,问:若b固定,要使半径为a的球面上电场强度最小,a与b的比值应为()。
A.1/3
B.1/e
C.1/2
D.1/4
A ______ of the long report by the budget committee was submitted to the mayor for approval.
A. shorthand B. scheme C. schedule D. sketch