C．

In most situations, light helps us see. But nowadays humans are using too much of it so that it is in fact a kind of pollution.

When it comes to looking at the night sky, too much light makes it difficult for us to watch some of life’s most wonderful sights: stars, planets and even galaxies(星系).

A．ccording to scientific research, about 2, 500 stars can be seen by the human eye without using any special equipment(设备). But because of light pollution, you can only see 200 to 300 stars from today’s countryside, and no more than ten stars from a city. In most big cities, people cannot see the sky filled with stars like they did in their childhood.

Light pollution affects more than just our view of sky. Research shows that lots of nighttime light can harm wildlife, too.

When birds fly to another place over cities, they sometimes get lost by the brightness and fly in circles(圈) until they drop from tiredness. Sea turtles(海龟) need dark beaches for laying eggs, but they can’t find their ideal places because of those bright lights.

Too much light at night may even affect human health, but scientists are not sure of that. They are still learning more.

In order to prevent things from going worse, governments and some organizations are working to reduce light pollution. Many cities and towns have taken action to reduce the use of lights at night. Lights are used only when and where they are truly needed. They also shine lights down at the ground instead of up into the sky and use lower brightness levels.

H．opefully, in the near future, humans can enjoy the clear and beautiful sky again and all the wildlife will live a peaceful and undisturbed life, too.

27. Why does the writer think that too much light is a kind of pollution?

A． Because there are fewer and fewer stars.

B． Because human health has been affected.

C． Because too much light is a waste of energy.

D． Because some of the wildlife can be harmed.