______ to looking after her sick mother for two years, she badly needed a holiday.

[      ]

A. Having devoted　　　　　　　

B. Devoted

C. To be devoted　　　　　　　

D. To have devoted

经腰椎穿刺将放射性药物如Tc-二乙三胺五醋酸（^99mTc-DTPA）注入蛛网膜下腔进行脑脊液间隙显像

A.流经通路

B.血管灌注

C.微血管暂时栓塞

D.血池分布

E.选择性浓聚器官摄取显像剂的机制分别是