题目选项分析

The recent increase in UFO sightings in the United States has alarmed many people, to cause them to speculate about the existence of extra-terrestrials here on Earth and to prompt fear of a government cover-up.

The recent increase in UFO sightings in the United States has alarmed many people, causing them to speculate about the existence of extra-terrestrials here on Earth and prompting fear of a government cover-up.