1 . For most of human history, the stars shone brightly in a dark night sky. But today, cities and towns, increasingly lit by artificial light at night, dramatically reduce the visibility of stars.

Satellite data suggests that light pollution has been increasing in many parts of the world over the last decade. However, satellites miss the blue light of LEDs (发光的二极管), which are commonly used for outdoor lighting, resulting in an underestimate of light pollution.

An international citizen science project called Globe at Night (环球夜景) aims to measure how everyday people’s view of the sky is changing. The data shows that the night sky got, on average, 9.6% brighter every year. For many people, the night sky today is twice as bright as it was eight years ago. The brighter the sky, the fewer stars you can see. If this trend continues, a child born today in a place where 250 stars are visible now would only be able to see 100 stars on his/her 18th birthday.

The main factors leading to increasing brightness of the night sky are industrialization and the growing use of LEDs for outdoor lighting. The loss of dark skies threatens our ability as astronomers to do good science. But everyday people feel this loss too. Starry night skies have inspired artists, writers, musicians and philosophers for thousands of years. Light pollution also has a bad effect on the daily cycle of light and dark that plants and animals use to adjust their lifestyle. Two-thirds of the world’s key biodiversity (生物多样性) areas are affected by light pollution.

Individuals and their communities can make simple changes to reduce light pollution. The secret is using the right amount of light, in the right place and at the right time. Making outdoor lights shine downward, using lights that give out more yellow-colored light instead of white light and putting on light timers can all help reduce light pollution. A view of about 2,500 stars in a truly dark sky might convince you that dark skies are a resource worth saving.

1. How is the first paragraph mainly developed?

A．By giving an example.	B．By making a comparison.
C．By reaching a conclusion.	D．By raising a question.

2. What do the figures in the third paragraph indicate?

A．The light pollution is getting more serious.

B．The night sky today gets darker than before.

C．It’s difficult to imagine a child’s fast growth.

D．LEDs are commonly used for outdoor lighting.

3. What does Paragraph 4 mainly tell us?

A．The bad effects of light pollution.	B．The factors causing light pollution.
C．The functions of starry night skies.	D．Key biodiversity areas in the world.

4. What is the purpose of writing this text?

A．To explain a phenomenon.	B．To suggest a solution.
C．To remember a scientist.	D．To increase public awareness.