心跳停止时间是指从循环停止到（）。
A.意识恢复
B.自主呼吸恢复
C.心脏自动节律恢复
D.重建有效人工循环
E.呼吸心跳恢复正常
参考答案：D
Which of the following statements about duration and convexity is FALSE（）
A. duration to first call is longer than duration to maturity.
B. convexity of a callable bond is always lower than that of a noncallable bond when rates fall.
C. callable bonds’ convexity can be negative.
各类地面航空无线电台和航空器无线电台的执照如停止使用，其电台执照应（）。
A.销毁
B.继续保留
C.转让给其他机场
D.上交回原发照机关
