John asked me ___I managed to do itA what B how C that 选B 我想问下为什么A不选?说明下这题的原因

John asked me ___I managed to do itA what B how C that 选B 我想问下为什么A不选?说明下这题的原因
John asked me ___I managed to do it
A what B how C that
选B 我想问下为什么A不选?说明下这题的原因

John asked me ___I managed to do itA what B how C that 选B 我想问下为什么A不选?说明下这题的原因
I managed to do it
句子完整了,do 后面有 it,如果没有可以.
John问我,我是怎样做到的.