she thik it is boring 过去式 think 和 is 为什么?

要变.宾语从句的从句时态必需与主句的时态保持一致.如果主句用过去式,则从句要用相应的过去式.比如：He said I was doing my homework.
所以这个句子变成过去式是：She thought it was boring.
只有当从句是客观事实的时候才不需要变,比如说 the sky is blue,the earth is round 等等这种永恒的东西,时态都是一般现在时

是的，因为她想的是过去的事

都要变
she think (that) it is boring
变过去式就是
she thought (that) it was boring
主句一定要变的，从句如果是客观真理（比如地球围绕太阳转这样的）仍用现在时
或者这句也可以说she thought(think) it boring 这就是动词+宾语+宾补的用法了

要变哦，既然是过去时，那么都要变化才能说明时态是变的。
She thought it was boring。