Passage 8

It was not until fairly recently that the secret of bats’ flight was solved, at least partially. The discovery of radar, the sending out of sound-waves and judging the obstacles ahead by the returning echo(回声), made some investigators wonder if this was not the system employed by bats. A series of experiments was conducted, and some fascinating things were discovered. First of all, some bats were blindfolded with tiny pieces of wax over their eyes, and as usual they had no difficulty in flying to and fro without hitting anything. Then it was found that if they were blindfolded and their ears were covered they were no longer able to avoid collisions（碰撞） and, in fact, did not seem at all keen on flying in the first place. If only one ear was covered they could fly with only moderate success and would frequently hit objects. This showed that bats could get information about the obstacles ahead by means of sound-waves reflected from them. Then the investigators covered the noses and mouths of their bats, but left the ears uncovered, and again the bats were unable to fly without collision. This proved that the nose, ears and mouth all played some part in the bat’s radar system. Eventually, by the use of extremely delicate（精密的） instruments, the facts were discovered. As the bat flies along, it emits a continuous succession of supersonic squeaks（吱吱声）, far too high for the human ear to pick up. They give out, in fact, about thirty squeaks a second. The echoes from these squeaks, bouncing off the obstacles ahead, return to the bat’s ear, and the bat can thus tell what lies ahead and how far away it is. It is, in fact, in every detail the principle of radar.

1.Which of the following does NOT play any role in the bat’s radar system?

A. Ears B. NoseC. Eyes D. Mouth

2.When their eyes and ears were covered, bats__________

A. still managed to fly fairly well

B. could fly with only moderate success

C. could not fly at all

D. were unable to fly without collision

3.Which of the following statements is NOT true?

A. There is still something about bats’ flight which scientists do not know.

B. Bats have their inborn radar systems.

C. Bats can fly successfully even in the dark.

D. It is the supersonic squeaks we hear that guide bats in flight.

4.The secret of bats’ flexible flight lies in the fact that bats____________.

A. have the ability to receive the echoes of supersonic sound sent out by themselves.

B. have the ability to receive the sound-waves emitted by the objects ahead.

C. are born with excellent flying skills

D. have good eyes which can see objects even in the dark.

5.The radar was invented__________.

A. on the basic of the experiments with bats.

B. According to bats’ flight principle.

C. before the discovery of the secret of bats’ flight.

D. after the discovery of the secret of bats’ flight.