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，请问A为什么不能选，还有这里的getting是分词还是动名词，
我真的分不太出来，谢谢