Do you know--------last night?Sorry,I don't know

Do you know--------last night?Sorry,I don't know
Do you know -------- last night?Sorry,I don't know.But I think he should go to bed early because he will have an English exam this afiernoon.
A.when he goes to bed
B.when he went to bed
C.when did he go to bed
D.when does he go to bed