Q2:

According to its proponents, a proposed new style of aircraft could, by skimming along the top of the atmosphere, fly between most points on Earth in under two hours.

1. According to its proponents, a proposed new style of aircraft could, by skimming along the top of the atmosphere, fly between most points on Earth in under two hours.
2. By skimming along the top of the atmosphere, proponents of a proposed new style of aircraft say it could fly between most points on Earth in under two hours.
3. A proposed new style of aircraft could fly between most points on Earth in under two hours, according to its proponents, with it skimming along the top of the atmosphere.
4. A proposed new style of aircraft, say its proponents, could fly between most points on Earth in under two hours because of its skimming along the top of the atmosphere.
5. According to its proponents, skimming along the top of the atmosphere makes it possible that a proposed new style of aircraft could fly between most points on Earth in under two hours.

choose A Why E is not correct?

统一，而且改变句子的重心。