the most important problem, a most important, most important 这三者之间有什么区别?
A. 副词 most 与二音节以及多音节的形容词连用构成最高级时, 必须带定冠词 (the most important problem): He was the most distinguished physician in Europe. 他是欧洲最杰出的内科医生。
B. 在 most 之前如果用了不定冠词 a，则 most 就不再是构成最高级的手段，而变成一种强化语了 (extremely, very):
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This is a most useful book. 这是一本极有用的书。
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He told me a most amusing story. 他给我讲了一个很逗人的故事。
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He is a most remarkable man. 他是一个很不寻常的人。
当 most + 形容词 + 复数名词时, most 也可能是强化语:
They are most useful alloys. 它们是极其有用的合金。
C. 如果 most 之前不带定冠词 the，也不带不定冠词 a，则从形式上看 most 既可以理解为最高级，也可以理解为强化语(extremely):
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Della is most efficient. (the most efficient of all 或 extremely efficient) (CGEL) 德拉办事能力最(很)强。
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You are most convincing. 你最(很)有说服力。
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She was most rude to me. 她对我最(很)粗鲁。
He had, in short, all the essentials for the portrait of ____ interesting and unusual young man.