Answer:
A. Alaska's oil pipeline is one of this country's greatest accomplishments.
Explanation:
Because it's correctly punctuated. The others don't make sense so.
Answer: The internet.
Explanation:
There are just too many advantages. The internet can provide information that teachers just can't give. Teaching is just a one man band, and what that one person knows is what that one person teaches. However, the internet collects data and knowledge from people all over the world. You have libraries, museums, and schools all in the palm of your hand.
A comma is used to show a short pause in a sentence