—Isn’t it a great surprise that I happened to meet my university English teacher at the South Bank Parkland last week?

—How long ____ you _____ each other, then?

A．hadn’t; seen

B．haven’t; seen

C．didn’t; see

D．don’t; see

有关MR血管造影论述，正确的是（）

A.适用于各种血管病变的检查

B.仅向血管内注射少量对比剂

C.无需向血管内注射对比剂

D.常用技术有时间飞跃法和相位对比方法

E.简单安全属于无创性检查