3.There are blue curtain.改 4.There are a desk,a table and a

1 There are blue curtain.改成There are blue curtains（名词变复数）.
2 There are a desk, a table and a shelf in it.改成 There is a desk, a table and a shelf in it.（there
be 句型谓语动词的就近原则）
3 There is a air_conditioner on the wall.改成There is an air_conditioner on the wall.（元音发音单词量词用“an”