Yet, people began to understand how electricityworks only a little more than two centuries ago.
然而，人们只是在两个世纪前一点才开始了解电的使用原理。
2
Yet, people began to understand how electricityworks only a little more than two centuries ago. Nature has apparently been experimenting in this field for million of years.
人们只是在两个世纪前一点才开始了解电的使用原理，自然界却显然在这方面经历 过了数百万年。
3
Yet, people began to understand how electricityworks only a little more than two centuries ago. Nature has apparently been experimenting in this field for millions of years.