I don’t know when my father _____ back, but I’ll let you know when he ___back.

A．comes, comes

B．will come, will come

C．comes, will come

D．will come, comes

上海证券交易所的运作系统常由交易主机、交易大厅、参与者交易业务单元或交易席、报盘系统及相关的通信系统组成。（）