three decades

• 三十年

three decades的用法和样例：

例句

1. Environmental awareness was non-existent three decades ago.
   环保意识在三十年前是不存在的。
2. What China has done in less than three decades is nothing short of astonishing.
   中国在短短三十年里所做的从来不乏令人惊异之举。