When I was a student in the university,I often thought about whether there ___ a way to prove P=NP.
问题描述：
When I was a student in the university,I often thought about whether there ___ a way to prove P=NP.
(P=NP是一个计算科学中的难解问题,现在都没有被证明)
这个题中应该填 is 还是 was?
我记得以前还学过这种句子：
I knew that the earth orbits the sun when I was young.
这个是用一般现在时，表示客观事实。
这两个句子用法有关系吗？
答
was
从句时态和主句保持一致
你这不是客观事实啊
我们常见的事实是：地球绕着太阳转
光速比声速快什么的