题目内容
（请给出正确答案）
[主观题]
A million years ______ but a brief span in the history of our planet.A．have beenB．areC．isD
A million years ______ but a brief span in the history of our planet.
A．have been
B．are
C．is
D．has been
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哪种类型不属于梅毒性心血管病
A．心肌受累
B．单纯性梅毒性主动脉炎
C．梅毒性主动脉瘤
D．冠状动脉口狭窄
E．梅毒性主动脉瓣关闭不全
