Many kinds of birds live in the United States, but the number of the birds is becoming smaller every year. One of the leading reasons is the growing number of pet cats. By keeping your pet cats in your home, you can help give birds a better possible chance to live.
Of the 90 million pet cats in this country, about two—thirds are allowed to go outside. It is said that these cats kill hundreds of millions of birds each year, as well as billions of small animals such as rabbits and field mice.
They can also bring illness to the animals that live in people’s yard(院子), further weakening the health of the natural populations.
Allowing pet cats to go outside is not just bad for birds and wildlife, it’s also bad for the cats themselves. Outdoor cats can get sick very easily. They are in danger from traffic and attacks(攻击)from other animals. In fact, outdoor cats usually don’t live past the age of five, while indoor cats often live to be 17 or older.
Keep your pet cat inside! If you raise a young cat, it’s your duty to let it play inside.

Problem	The number of birds is becoming ________; at the same time，many pet cats are in _______from traffic and attacks from other animals．
Reason for the problem	Pet cats are_________to go outside freely．
What to do	People who_________ a young cat have the________  to let it play inside．