一些词义相近的词语求辨析
第一问：Which one would you pick up?Then give your (reasons/causes）.
答案给的是reasons,请问为何causes不可?在百度词典中对它的解释中存在“理由,缘由”.
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第二问：After the test used by a company to enroll fresh blood,Only one of two hundred people was (accepted/hired).
答案给的是hired.请问为何accepted不可以?同样是在百度词典中,对accpet的第六个解释为“招收,接纳（求职者、会员等）”
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第三问：Every acquaintance of mine (considered/regarded) it as the best answer.
答案给的是regarded.
我觉得如果用consider也可以啊,是不是因为regard sth as .这个固定搭配更常用,并且没有consider sth as ...这种用法?
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第四问：Every acquaintance of mine regarded it as the best answer but nobody realized it (just then/at first).
答案给的是at first.
请问为何不能用just then,在那时（指最佳答案被说出之前）呢?