— What do you think of the service here? 

— Oh, wonderful! We ____ a better place.  [ ]

A. couldn't have found

B. won't find

C. mustn't have found

D. oughtn't to have found

飞跃时间(TOF)法MRA显示血管的主要机理为

A．使用了特殊的表面线圈
B．使用了特殊的射频脉冲
C．使用了较长的TR
D．流动血液和相位变化
E．流入扫描层面的未饱和血液受到激发