"Các chiếc ghế" and "các cái ghế" would be accepted. It is probably not added yet. Next time, if you encounter this phrase, you should report it to Contributors so that they could add it into database.
FWIW I whinged about this to my gf who is a native Vietnamese speaker, and she said các sounds wrong to her in this case. I wish the course did a better job of teaching which plural words are acceptable in which contexts though.
My determination is "những” could replace “các” in some cases. "Các” is used for the identified plural subject(boys and girls, ladies and gentlemen, cats and dogs), but it is not used if the identity of the following noun is inanimate.