Thank you for sending us ____ fresh vegetables of many kinds. You have done us ____ great service.

A．不填；a

B．the；a

C．不填；不填

D．the；不填

《国务院关于预防煤矿生产安全事故的特别规定》规定：煤矿企业是预防煤矿生产安全事故的责任主体。