求一篇英语的抠词填空......

Sometimes people make mistakes when they say they have s__ __ UFOs.

Many people today read stories a___1___ UFOs. But what are UFOs? The most popular explanation（解释）for UFOs is that to carry visitors coming from other planets. They can fly m__2__ faster than planes on the earth. Some UFO scientists b__3__ this explanation. They even believe that a few UFOs have reached the earth and the space visitors are living around us.
Sometimes people make mistakes when they say they have s__4__ UFOs. They may see a weather balloon, or a strange plane, or the light which comes f__5__ the ground. However, there are a lot of other things we cannot explain. It may t__6__ many years to find a clear answer.

about, much, believe, seen, from, take