hi,
i just saw a USA city called seattle on tv, and comparingly with other metropolitan cities around the world like singapore, new york etc, it has hardly any plants, nor shrubs nor any trees in its total surrounding areas. So how does the concrete city of seattle breathes fresh air, if there is no vegetation. Haven't you learnt in biology that photosynthesis in plants, trees leaves produces oxygen needed for the survival? Or do people of seattle breathe in pollution carbondioxide, vehicle emmissions and other affluents???