An idea suddenly came to J.K.Rolling ________ she could write a book about people living in the magic world

A．if

B．when

C．that

D．which

3D-CE-MRA的应用不包括（）

A.主要用于颅脑大面积血管病变

B.可在不同期相观察到动脉或静脉病变

C.亦可作减影显示病变

D.需注射顺磁造影剂

E.仅血流呈高信号