the most + 形容詞 + 名詞 + + 主詞 + have ever + seen any pollution. 使用太陽能的優(yōu)點是它不會制造任何污染。

　　八、The reason why + 句子 ~~~ is that + 句子 (...的原因是...)

　　例句：The reason why we have to grow trees is that they can provide us with fresh air./ The reason why we have to grow trees is that they can supply fresh air for us. 我們必須種樹的原因是它們能供應我們新鮮的空氣。