题目内容：

    GPS has completely transformed how we get around. But other animals have long had their navigation (导航) systems built right in --- like ants and bees.

“We know their eyes are quite sensitive to polarized light (偏振光), and the sky has a particular pattern of polarized light, connected with the position of the sun.” says Barbara Webb, a bioroboticist at the University of Edinburgh. You can see polarized light firsthand if you take a pair of polarized sunglasses and spin them against the sky --- the light passing through the lenses changes. Webb says the insects have polarization like that built into flat sides of their compound eyes. “You can think of it as the equal of having a little polarization directional filter (滤镜) over them or lots of sunglasses pointed in different directions.”

But Webb was curious about whether there's really enough information in the sky to give insects an accurate sense of direction. So her team built a sensor modeled after a desert ant eye and put it under artificial light meant to simulate the sky. They then fed that sensor input into a model meant to copy the brains of desert ants and other insects with a sky compass. And they found that with the insects' natural sensing and processing equipment, they can likely sense compass direction down to just a couple degrees of error.

A system based on that of insects could someday be a cheap, low-energy alternative to GPS. “Insects have very tiny brains, a brain that's using hardly any energy. And yet they're still able to navigate better than we can with GPS, which is a huge system.” Webb is now working on building a robot that can, like the desert ant, use light to get its direction. Although after sundown, it may have to ask for directions.

1.What make(s) it possible for ants and bees to sense the direction?

A.Flat eyes. B.Polarization.

C.A directional filter. D.Polarized sunglasses.

2.Why did Webb and her team build a sensor?

A.To copy the brains of desert ants.

B.To model after the desert ant eye.

C.To satisfy their desire for answers.

D.To test an accurate sense of direction.

3.What is the future navigation system supposed to do?

A.To save energy. B.To be a substitute for GPS.

C.To guide the blind. D.To help GPS work better.

4.What is the main purpose of the passage?

A.To introduce an invention.

B.To praise a scientific achievement.

C.To present new scientific findings.

D.To encourage people to learn science.