This is chair/This is a chair.这两句哪一句是错误的?

This is chair/This is a chair.这两句哪一句是错误的? is this her chair的同义句 This chair is orange.(改成同义句) whoes is this chair?（同义句） what is this?______ a chair. Is this chair made ( ) wood? this chair is made of( ) What`s this?回答是This is a chair.还是It`s a pencil. There is no chair in this room.(同义句) “There is a chair in this room,isn't there?”是简单句、并列句还是复合句? this chair is very ( ).Please find a clean one. Is this chair[she her hers]?