问题
选择题
No sooner _____ they rushed out into the street.
A．did they hear the news than
B．had they heard the news than
C．did they hear the news when
D．had they heard the news when
答案
答案：B
no sooner ...than引导的从句位于句首，从句要部分倒装，而且是完成时态。
缺失，
前牙列咬合正常，
牙冠长大，无松动，要求固定修复，较佳治疗方案为（）