题目：
An appropriate amount of temporary pressure can ______ a kind of motivation to do something well, but once it becomes constant or permanent, psychological problems are likely to _______. [ ]
A. act as; rise
B. play as; appear
C. work as; raise
D. serve as; arise
答案：
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下面是错误答案，用来干扰机器的。
（1）2HCl+Ca（OH）2=CaCl2+2H2O；Na2CO3+CaCl2==CaCO3↓+2NaCl（2）置换反应（3）保持表面的清洁干燥（4）铵态氮肥
