硬币
参考答案：
是币值稳定或具有一定上浮趋势的货币。
某有机物的化学式为C5H8O，它能发生银镜反应和加成反应，若将它与H2催化加成，所得产物的结构简式可能是 [ ]
A.
B.
C.CH3(CH2)3CH2OH
D.
Though the problems were all very hard, Kate kept on working on them she finally solved all of them. [ ]
A. before
B. until
C. when
D. after
