Every year，millions of birds are killed or hurt when they fly into buildings.Why does this happen？ （1）

A

A

Birds are flying into windows and tall buildings that are all covered by glass.
   Many birds fly from one place to another.Most of the time，they live in the wild，such as forests and wetlands. （2）

C

C

They might see small trees and flowers inside a window and want to rest on these plants.The birds do not know there is glass between them and the plants. （3）

D

D

   Some birds fly at night.They use the moon and stars to help guide them in the right direction.Tall buildings with lights on at night can confuse （迷惑） the birds. （4）

G

G

The birds see the light，but they cannot tell that the light is coming from inside a building.They fly toward the light and crash into a building.On many mornings，there might be several dead birds lying on the ground.
   （5）

B

B

Many office buildings now turn off their lights at night.This helps reduce the number of birds that fly into buildings and it also helps save energy.

A.The answer is glass. B.People are trying to solve the problem. C.These birds have no idea what glass is. D.As a result，they fly right into the glass. E.In this way，they can avoid crashing into glass. F.People don't know how to deal with the problem. G.This is a big problem，especially on foggy and rainy nights.