The sign on the birds' cage is interesting.is为什么要改成are

连词成句 the sign does bird’s on mean the cage I saw a bird singing on the sign.（否定句） 'danger',the,sign,building,on,the,means(.) the sign on the grass是什么意思 Does the sign on the cage interesting? The sign on the front door(　　):Push The sign on the wall___we must stay away from it. The sign on the wall___we there a sign on the chair on mondaythere a sign on the chair on monday point to a sign on the sign on the door什么意思 Just like a bird,fly on the The bird is singing on the t_____ of the house. The sign on the wall___we must stay away from it. 选择题：（ ）The sign on the wall _____ 'No smoking'. is ,panda ,on ,sign ,interesting ,the ,cage ,the .排列顺序 The sign on the birds' cage is interesting.怎么改 The sign on the birds cage is intereting一般疑问句 the sign on the wall _( mean)'no parking.