《高考考试必刷题》里的一道改错题：In 1752,Benjamin Franklin tied a key to a kite and flew it in a storm with the aim of finding out that lightning was a form of electricity.
这里的“闪电是电的一种形式”不是客观事实吗？为何不把was改成is？
In 1752,Benjamin Franklin tied a key to a kite and flew it in a storm with the aim of finding out that lightning was a form of electricity.
In 1752,Benjamin Franklin tied a key to a kite and flew it in a storm with the aim of finding out that lightning is a form of electricity.
两种时态都对。一般过去时，重点不在考虑是不是“客观真理”，只不过为了“时态呼应”；一般目前时，着重暗示这是一种客观现象，不受时间制约，给人感觉是为了寻求真理。