How to raise the efficiency, ______ is the question.
A. what
B. which
C. that
D. if
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Why did Spring sell his false autographs in England and Canada
A. There was a greater demand there than in America.
B. There was less chance of being discovered there.
C. Britain was Spring's birthplace.
D. The prices were higher in England and Canada than the ones in America.
以下不与7,8-二羟基香豆素类化合物发生反应的试剂是( )
A. 异羟肟酸铁试剂
B. Gibbs试剂呈阳性
C. Emerson试剂呈阳性
D. 碱试液反应
E. 稀盐酸
若磁盘的转速提高一倍，则 (8) 。
A. 平均寻道时间减半
B. 平均存取时间减半
C. 平均寻道时间不变
D. 存储道密度提高一倍
某关系表中定义了“姓名”、“性别”、“年龄”、“身份证号”4个字段，其中 (59) 字段较适合作为此关系表的主键。
A. 姓名
B. 性别
C. 年龄
D. 身份证号
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