SAT语法题,

SAT语法题,
1.The library is (older than it but still just as beautiful as the courthouse.)
真确答案为括号中的部分应该改为older than the courthouse but just as beautiful.但是as beautiful后面不加其他的感觉很别扭,不是应该都是as beautiful as ...
2.(In similarity with) some other great works,the enduring horror tale Frankenstein was first published anonymously; its author,Mary Shelly,wrote the novel when she was not quite nineteen years old/
括号中改成Like,虽然感觉很顺,但是这样没有平行结构的错误吗?为什么不能是Like what happened with呢
3.The Amazon River carries more water than( the water carried in any of the world's other rivers.)
any other river in the world ,为什么不能是the water carried in any of the world's other rivers,我平行结构一直不是很搞的懂,能不能顺便给我讲解一下呢?