For reasons of security the door is always kept locked.

　　為了保證安全，門(mén)總是鎖著(zhù)的。

　　The agreement will open the door to increased international trade.

　　此協(xié)議將會(huì )提供增加國際貿易的機會(huì )。

　　The government's policy is an open door to disaster.

　　政府的政策為災難敞開(kāi)了大門(mén)。

　　There's building work going on next door.

　　鄰居正大興土木。