根据短文内容回答问题!A lift is very useful.It looks like a small room.

根据短文内容回答问题!
A lift is very useful.It looks like a small room.It goes up and down all day.Sometimes a worker stands in the lift.He or she operates（操作） it up and down.In modern lifts there's no worker.People walk in.They know what floor they want to go.They push a button(按钮)and the lift goes to that floor.It's very fast and easy.
Lifts are very important to us.Why?Think about a tall building.Maybe it has twenty floors.Maybe it has fifty or more.Who can walk up all the stairs(楼梯)?Maybe people can climb them once.Can someone climb thirty floors to an office every day?Can small children walk up to their rooms on the twenty-four floor?Can their mothers or fathers carry food up to all those stairs?Of course not.We can have very high buildings because we have lifts.We could not have all the beautiful tall buildings without lifts.Because it is too tired for people to climb the stairs every day.