There are some birds in the tree.There are some pears on the tree.为什么前面用in后面用on?

There are some birds s___in the tree. There are some birds singing( )the trees There are some birds in the trees对some birds 提问 There are some birds in the sky改一般疑问句 There are some birds in the tree.改为一般疑问 There are some birds on the tree.的否定句 There are some birds in the tree改为一般疑问句 There are some birds on the tree.的一般疑问句 如：There are some birds in the picture There are some birds in the tree.对what提问 There are some birds ( )the tree and there are some apples( )the tree There are some birds in the picture.(改为一般疑问句句)__________ there ___________ birds in the picture? There are some brids in the tree.(对some birds提问 括号里要填in还是on?There are some apples and some birds ( ) the tree. there are some apples---the tree,there are some birds----the tree.(in on at )请选择 There are some birds in the picture怎么改否定There are some birds in the picture怎么改否定句, There are some birds in the tree,______?A.is there B.isn't c.are there D.aren't There are some birds in the tree(改为否定句）