1、There is a front and a back entrance to the theatre.
這家劇院有一個前門和一個后門。

2、Here the air and water discharged from the return valve to the back entrance of the impeller.
在這里空氣排出而水又從回流閥返回到葉輪入口。

3、There is a front and a back entrance to the house
這所房子有一個前門和一個後門

4、We used the back entrance to the building.
我們是從大樓的后門入口走進去的。