that
问题描述：
that
1.H was the author of more than 100 books for boys in the second half of nineteenth century {that} focused on the theme of success coming to those who work hard to achieve it.
2.What they share in common,however,is the extraordinary variety of plant and animal life-forms {that} are a necessary part of the ongoing process of their fomation.
答
1.that 引导定语从句,修饰先行词books,即that指代more than 100 books .
that作定语从句的主语
2.that 引导定语从句,修饰先行词plant and animal life-forms ,即that指代plant and animal life-forms ,that作定语从句的主语但是我搞不清第一题that为什么不指代author或boys,他们也可以focus on theme 第二题为什么不是指代variety