[考題] 不定詞與動名詞(現在分詞)

[ambrosio (...)]

We knew that Adam should study ver hard and get high grades in school
if he wanted to become a doctor.
We all laughed at the idea of Adam ____ high grades.
Adam got mad at us and said he would become a doctor and prove us wrong.

  (A) to get   (B) getting

 答案是B，請問A為什麼不能選，還有這裡的getting是分詞還是動名詞，
 我真的分不太出來，謝謝

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推 lang0720:動名詞是名詞 現在分詞是形容詞
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