虚拟语气 i didn't know his telephone number.---- it,I ------ the

虚拟语气 i didn't know his telephone number.____ it,I ______ then
i didn't know his telephone number.____ it,I ______ then
A.Had I known; would ring him up
B.Should I know ;would have ring him up
C.If I knew ;would ring him up
D.Had I know; would have rung him up