18 世纪中叶，电学家富兰克林做了多次实验，进一步揭示了电的性质，并提出了（）这一术语。
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“伏打电池”是由一系列圆形（）和（）相互交迭而成的装置。
A. 锌片
B. 铜片
C. 银片
D. 石墨
Many young married couples are wondering ___.
A. that they should buy or just rent an apartment
B. which they should buy or just rent an apartment
C. what they should buy or just rent an apartment
D. whether they should buy or just rent an apartment
Please get the discussion ___. Time is limited.
A. at track
B. in track
C. on track
D. for track
Water conservation is not only ___ our economy but also a task of strategic importance.
A. in the interest of
B. on the point of
C. around the corner of
D. in the absence of
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