How can it matter if I leave one little tap running, one little light on or leave a little piece of litter on the road? And anyway, no one will know.” Of course, it wouldn’t matter if there were just a few people in the world. But just think of all the millions of people     1    (say) to themselves: “It doesn’t matter. It’s just me. And, anyway, no one knows.” Millions of gallons of water would     2    (waste); millions of lights would be left on; millions of pieces of litter would be dropped. And all of this would be very     3    (harm).