在选择钢丝绳的安全系数时，应按以下原则（）选用。
A.与重物的质量相等；
B.安全、经济；
C.经济；
D.安全。
参考答案：B
The food ________ because it _________ good.
A． sold out soon; was tasted
B． was soon sold out; tasted
C． has soon sold out; tasted
D． will soon sold out; tasted
母亲妊娠晚期患急性乙型肝炎时，胎儿感染率为
A．25%B．50%C．70%D．85.90%E．100%
