Question

Could you please tell me _______________ you know about the accident（事故）?

A
that
B
which
C what D
why

Answer 1

C what
tell sb. sth
现在的sth.是由what 引导的宾语从句
what you know about the accdient

what 在这从句中也充当宾语成分，还原是 you know sth. about the accdient

Answer 2

c
什么