but there is another thing you must remember it.为什么不加it?

题目

but there is another thing you must remember it.为什么不加it?

答案

这是个定语从句,省略了that .这样看吧,通俗点：
but there is another thing.还有另外一件事
you must remember it.你必须要记住它.
它 （it ）指代的就是这件事.
两句合并,就要省略一个,否则就重复了啊