I really don’t know _______I kept the secret papers.

A. where was it　

B. it was where that

C. where it was that　

D. where was it that

I really don’t know ___ ___I kept the secret papers.

 I really don’t know _______I kept the secret papers．

       A．where was it                                  B．it was where that                    

       C．where it was that                             D．where was it that

I really don't know________ I kept the secret papers.

[　　]

．I really don’t know _______I kept the secret papers．