题目内容：

Have you ever pressed the pedestrian button at a crosswalk and wondered if it really worked?  They’re called “placebo(安慰剂）buttons”一buttons that mechanically sound and can be pushed，but provide no functionality.

In New York City, only about 100 of the 1, 000 crosswalk buttons actually function. Crosswalk signals were generally installed before traffic jam had reached today’s levels.

But while their function was taken over by more advanced systems—such as automated lights or traffic sensors — the physical buttons were often kept, rather than being replaced at further expense. Other cities，such as Boston，Dallas and Seattle，have gone through a similar process, leaving them with their own placebo pedestrian buttons. In London, which has 6, 000 traffic signals，pressing the pedestrian button results in a reliable “Wait” light. But that doesn’t necessarily mean that the “green man”— or “pedestrian stage” in traffic signal design profession — will appear any sooner.

“We do have some crossings where the green light comes on automatically, but we still ask people to press the button because that enables accessible features,’’ said Glynn Barton, director of network management at Transport for London.

These features, such as blind tracks and hearable traffic signals, help people with visual disorder cross the road and only function when the button is pressed. As for the lights, a growing number of them are now combined and become a part of an electronic system that detects traffic and adjusts time frequency accordingly (giving priority to buses if they’re running late, for example), which means that pressing the button has no effect.

According to Langer, a Harvard psychologist, placebo buttons give us the illusion (错觉)of control — and something to do in situations where the alternative would be doing nothing. In the case of pedestrian crossings, they may even make us safer by forcing us to pay attention to our surroundings. “They serve a psychological purpose at the very least,” she added.

1.Why are the physical buttons still kept in some cities?

A. Because it may cost money to replace them.

B. Because they remain as memories of a city.

C. Because do have real functions in traffic.

D. Because they can result in reliable lights.

2.Which of the following word can replace the underline word “features” in Paragraph 4?

A. Functions.

B. Uses.

C. Equipment.

D. Facilities.

3.If you pressed a “placebo button” in London, what would happen?

A. All traffic would be affected.

B. Some kind of sound might appear.

C. Pedestrians came first to cross the road.

D. “Green man” were bound to show up earlier.

4.What can we know about “palcebo buttons” from Langer’s words?

A. They can really control traffic.

B. They serve little functions.

C. They may work mentally.

D. They can help the blind.