The tables and pictures help make clear I wasn't sure of before.
A. it; for me to understand what
B. it; everything
C. everything; to understand what
D. /; what
网友回答
(答案→)A. it; for me to understand what
B. it; everything
C. everything; to understand what
D. /; what
解析：it为形式宾语，后面的不定式作真正的宾语，what从句为宾语从句，what又在宾语从句中作of的宾语。