请教but 和 while 的区别

我记得好像but不能象while,when这种词直接加状语的省略形式.

但是在作题中有的题目确实有but 后面直接加分词省略主语的情况,自己对but和while的区别不是很清楚

那位NN能给说说but和while到底怎么用呢?

Seldom more than 40 feet wide and 12 feet deep, but it ran 363 miles across the rugged wilderness of upstate New York, the Erie Canal connected the Hudson River at Albany to the Great Lakes at Buffalo, providing the port of New York City with a direct water link to the heartland of the North American continent.

1. Seldom more than 40 feet wide and 12 feet deep, but it ran 363 miles across the rugged wilderness of upstate New York, the Erie Canal connected

2. Seldom more than 40 feet wide or 12 feet deep but running 363 miles across the rugged wilderness of upstate New York, the Erie Canal connected

3. It was seldom more than 40 feet wide and 12 feet deep, and ran 363 miles across the rugged wilderness of upstate New York, but the Erie Canal, connecting

4. The Erie Canal was seldom more than 40 feet wide or 12 feet deep and it ran 363 miles across the rugged wilderness of upstate New York, which connected

5. The Erie Canal, seldom more than 40 feet wide and 12 feet deep, but running 363 miles across the rugged wilderness of upstate New York, connecting

讨论的答案是B, but running 这句是不是省略了主语呢?

but running跟前面的seldom more than平行，一起做状语修饰the Erie Canal.

but后面接的不是从句而是并列成分。

while后面接的是状语从句。

when/while/if 等其他条件状语的可以直接+形容词/分词/完整句

but不能用作条件状语的省略.

but running 能做状语从句的省略形式吗??

but 和while一直很晕