2011年成考專升本英文寫作必背句型(8)

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(yīng)我們新鮮的空氣。