Oxigen vs Carbon Dioxide

This is what YJ told me: Plant a lot of trees is very good. Trees dont want is oxigen. Trees want is carbon dioxide. People want is oxigen. People dont want is carbon dioxide. (He is beside me and ask me to type what he says.)

This is exactly what YJ told me. The grammar... eerrr... direct translate from mandarin!! I correct him, and he asks me to delete the "is". But, I just like to keep it, let him see later when he grows up. :-)