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问题 填空题

用反证法证明命题“在直角三角形中，至少有一个锐角不大于45°”时应第一步先假设所求证的结论不成立，即为______．

答案

“在直角三角形中，至少有一个锐角不大于45°”时应第一步先假设所求证的结论不成立，即为：两个锐角都大于45°．

故答案是：两个锐角都大于45°．

单项选择题

The nurse teaches the parents of a child being treated with antibiotics for an ear infection for a follow-up visit after the child completes the course of therapy. Which of the following statements by the parents indicates that they understand the reason for the follow-up visit

A. "Her hearing needs to be checked to see if the infection has done any damage. "
B. "The doctor wants to make certain she has taken all the antibiotics. "
C. "We need to make sure that her ear infection has completely cleared. "
D. "She needs to get another prescription for second course of antibiotics. "
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问答题 简答题

简述根结线虫的致病机理。
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