双胎妊娠腹部听诊，两个胎心影每分钟
A．2次以上B．5次以上C．8次以上D．10次以下E．10次以上
参考答案：E
He's never been to a foreign country, ________?[ ]
A. isn't he
B. is he
C. has he
D. hasn't he
论大规模分布式系统缓存设计策略
