1·I guess farming is about the cleanest way to make a living.
我觉得经营农场大约是最清洁的一种谋生方式了。
2·London (left) : Renowned for centuries for its infamous smog and severe pollution, the city today has the cleanest air that it has had since the Middle Ages.
伦敦(左图)：在过去几个世纪，这座以其雾霭和严重污染“闻名遐迩”的城市，却有着从中世纪以来乃至今日都最清洁的空气。
3·The police are professional, even enforcing laws on litter to make Rwanda the cleanest country in Africa; plastic bags are confiscated at the airport.
国家的警察部门更加专业化，他们甚至会对垃圾管制而执行法律，以使卢旺达成为非洲最清洁的国家；塑料袋在机场也全部没收。
4·In the event of a fire, remember the cleanest air is closest to the ground.
一旦发生火灾，记住要清洁地面附近的空气。
5·It is known that photovoltaic system is one of the cleanest, most practicable, most promising resource in all kinds of renewable energy resources nowadays.
太阳能发电是当今世界上可再生能源领域中最清洁、最现实、最有大规模开发利用前景的发电方式之一。