蛛网膜下腔阻滞治疗癌性疼痛，是属于哪种方法（）
A.放射疗法
B.物理治疗
C.介入疗法
D.手术疗法
E.药物疗法
参考答案：C
柴油机空气滤芯脏，进气量不足，可能导致排气冒（）。
A.黑烟
B.白烟
C.蓝烟
D.灰白烟
No one has come up with a better explanation of why dinosaurs _____.[ ]
A. died away
B. died for
C. died of
D. died out
