题目内容

所有的肽和蛋白质都能和硫酸铜的碱性溶液发生双缩尿反应

A. 对
B. 错

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He saw it as his d ________ to help the poor.

A. duty
B. dress
C. done
D. dry

Try to s________ every opportunity to practice English.

A. search
B. see
C. seek
D. son

For most students, studying a is a ________ wonderful experience.

A. along
B. alone
C. always
D. abroad

There’s a gun in pr ________ every American home.

A. practically
B. practical
C. poor
D. proof

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