Questions 7-15. Read the passage about UFOs and choose True or False for each sentence.

An unidentified flying object (UFO) is any light or object seen in the sky that can't be explained. Hundreds of UFO sightings are reported every year. More than nine-tenths of them are later identified as ordinary objects. They turn out to be planes, satellites, or planets. Others are later identified as balloons, kites, clouds, or birds. But some are deliberate fakes.

UFOs have been reported since ancient times. Modern reports of UFO sightings began in 1947. Some observers reported seeing saucer-like shapes in the sky. Since then, UFOs of any shape are often called flying saucers.

The United States Air Force took these reports seriously. Air Force officials did not necessarily believe in visitors from outer space. They wanted to be sure that UFOs were not a threat to America. A UFO might, for example, be an enemy airplane.

Project Blue Book was the Air Force's program for investigating UFOs. It ran from 1947 through 1969. The Air Force investigated 12,618 UFO sightings. All but 701 were identified.

The Air Force concluded that UFOs were no threat. All sightings could be explained by science. There was no evidence that UFOs came from other planets.