在SE序列中,射频脉冲激发的特征是( )
A.α<90°
B.90°—90°
C.90°—180°
D.90°—180°—180°
E.180°—90°—180°
参考答案:C
Duty is an act or a course of action that people _____ you to take by social customs, law or religion. [ ]
A. persuade
B. request
C. instruct
D. expect
心脏病患者最易并发感染性心内膜炎的情况是()
A.心力衰竭
B.心房颤动时
C.患严重二尖瓣狭窄时
D.咽喉炎症或行口腔手术时
E.患室间隔缺损时