there is a boy ( ) a yo

Behind every successful boy,there is a There is a boy ( )at the door. There is a boy in the picture there is a boy standing on the tree 可以改成there is a boy to st There ( ) a boy and some apples.A is B are One boy is a boy There is a boy and two girls in the classroom There is a boy in the（ ） on the wall There is a boy under the tree,怎样改为疑问句 (a book / the boy / there / reading / over )is my brother The boy standing there is a classmate of mine. There is a boy under the big tree