Think about it. That little boy who's running back into his house, he may have a nice, clean fresh water supply, but he's got dirty hands that he's going to contaminate his water supply with.
例えばさっきの少年が 家に帰ってきれいな水があればと 考えてみてください しかし現実は自分の汚れた手で 飲み水を汚染してしまいます