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问题 单项选择题

主动脉瓣关闭不全：

A．颈部和锁骨上窝
B．左腋下和肩胛下区
C．胸骨左缘和心底部
D．胸骨左缘和心尖部
E．心尖部
下列各心脏病变所产生的杂音可以传导至

答案

参考答案：C

选择题

Mary had to wok at evenings and weekends. Only in this way _____ able to complete the report

by the deadline.[ ]

A. was she

B. she was

C. had she been

D. she had been
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选择题

许多科学家认为，“厄尔尼诺”现象的产生是由于(    )

A．东北信风的减弱

B．东南信风的减弱

C．东北信风的增强

D．东南信风的增强
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