题目内容：

If you thought pilots dimmed（调暗）the lights before takeoff to give you some shuteye, think again. Believe it or not, the dim lighting could actually help save your life in case of a plane emergency.

The dimmed lights before taking off the runway and landing are a flight precaution used to help passengers’ eyes adjust quicker during an emergency escape. “Going from a brightly lit environment to one that’s completely dark would require some time for our eyes to focus and see the escape slide,” Alice Theriault, service director for Air Canada wrote in a press statement. “Since we need to have all the seconds on our side in the event of an emergency, dimming the lights is one of many steps we take to ensure the safety of our customers.”

The phenomenon that your eyes see those strange speckles (小斑点) as your sight adjusts to a dark place after being in a light place is called dark adaptation. It normally takes our eyes about 20 to 30 seconds to see best in a dark room. The brighter the lights, the longer it takes for our eyes to adjust, which is why dimming the plane lights could shorten your “dark adaptation” time since you haven’t been sitting under fluorescent bulbs (荧光灯) all flight.

Not only does dimming lights add valuable time to the escape process, but it reduces the tension on your eyes if you need to look outside, or see the emergency lighting along the passage. “It helps keep you in the right direction.” Patrick Smith, an airline pilot and author of Cockpit Confidential told The Telegraph. “It also makes it easier for flight attendants to assess any outside risks, such as fire or debris, that might affect an escape.” So next time a pilot dims the lights, just know it’s for your safety, even though it creates a gentle atmosphere for your takeoff into the sky.

1.The lights are turned down before takeoff to help passengers_______.

A. escape in time of emergency

B. take a short break

C. create a comfortable atmosphere

D. enjoy themselves

2.Which of the following is True according to Paragragh 2 and 3?

A. Dimming lights is required when accidents happen.

B. Our eyes need some time to adapt to the change of light.

C. Speckles are caused by the use of dimmed lights.

D. It is required for pilots to turn off lights during the flight.

3.What is the function of shortening “dark adaptation” time?

A. Slowing down the landing.

B. Adjusting the plane lights.

C. Keeping passengers calm.

D. Helping the crew judge outside risks.

4.What is the text mainly about?

A. A tip to make air travel safer.

B. An emergency event happening on a plane.

C. An explanation of an airline safety measure.

D. A warning message from the pilot.