What is the function of the first co?
alfredo_555 is correct. I would also like to add that you could omit the có in this sentence. It would still make sense, but it is more proper if you kept the có.
Hi can you explain for me ,why does not use (the grass )
Using "the" implies that we are referring to a specific patch of grass or a specific kind of grass. Without the article "the", we are referring to grass in general.
Có is to used to form a question. For example: Bạn có khoẻ không (Are you healthy?), Tôi khoể (I am healthy).