One must realize that it takes years for a planted tree to mature and years to clean out a polluted river.

人们必须认识到，一棵树要长大成荫得好几年，一条河要变干净也需要很多年。

youdao

One must realize that it takes years for a planted tree to mature and years to clean out a polluted river.

人们必须认识到，一棵树要长大成荫得好几年，一条河要变干净也需要很多年。

youdao