Time which would be better spent tackling the great problems!

题目

Time which would be better spent tackling the great problems!
Ramona pointed out that I've been wasting-20 minutes a dy standing on cafeteria lines,Time which would be better spent tackling the great problems.
各位大侠,上面“which”的作用是什么?,这是个什么从句?
可以不要吗?
还请详细解释一下
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对下面几位的回答不是很满意，麻烦哪位再解释一下吧

答案

which 是定语从句中的关系代词.它有两个作用,一是起到连接作用,把定语从句与主句连接起来；二是在定语从句中充当成分,作主语,不能不要.因为关系代词在定语从句中,充当主语时,关系代词不能省略.