术前应行哪项检查有助于诊断：
A．B型超声波检查
B．腹部X光片检查
C．妇科PV检查
D．宫颈刮片
E．宫腔镜检查
参考答案：A
将一枚硬币连续抛掷3次，正面恰好出现两次的概率为______．
I want to thank my friend John, without _____ help, I wouldn't have been saved.
A．his
B．whose
C．whom
D．Which
