谁能帮我分析一下这句话的语法结构!

题目

谁能帮我分析一下这句话的语法结构!
there is only roughly a fifth of the krill around now that were around in the mid-70s.

答案

算是个there be结构的主语从句吧,
that were around in the mid-70s中的that指代的是前面的the krill ,即本句的主语,作用修饰前面的内容.
主句是there is only roughly a fifth of the krill around now ,there be句型作为主句,即整个句子分为两部分.