I know only a little about this matter ,you

答案A
whoever 引导主宾表从句,whoever在从句中做主宾表,这个句子恰恰从句做ask的宾语,whoever在从句中做主语
B.whomever 在从句中做宾语,而题干中缺的是主语
C.anyone 后面要加who,形成who引导的定语从句
D.the one 也要加who