莱氏（Ledley）于哪年首先设计成全身CT装置（）
A.1969
B.1972
C.1973
D.1974
E.1978
参考答案：D
Owing to environment pollution, a number of insects have ________. [ ]
A. died out
B. put out
C. brought out
D. picked out
SDH帧的结构开销分为（）。
