GMAT语法问题求救！！！

jm2003222

Seldom more than 40 feet wide and 12 feet deep , but it ran 363 miles across the rugged wilderness of  upstate New York, the Eric Chnal connected the Hudson River .......是OG上的题目。

问：1。DEEP后有了逗号后，第一句成为了修饰句，它就一定要修饰BUT吗？不能与第二句联合起来修饰Erie Canal吗？

  2. but 有没有对称原则？



还有一题：It will not be possible to implicate melting sea ice in the coastal flooding that many global warming models have projected.

问：that 修饰什么？修饰coastal flooding吗？



还有我刚开始看G，语法题对了8个，学一个月去考可以吗？



谢谢！