Americans use many expressions with the word dog. People in the United States love their dogs and treat them well. They take their dogs for walks, let them play outside and give them good food and medical care. However, dogs without owners to care for them lead a different kind of life. The expression, to lead a dog's life, describes a person who has an unhappy life. 
Some people say we live in a dog-eat-dog world. That means many people are competing for the same things, like good jobs. They say that to be successful, a person has to work like a dog. This means they have to work very, very hard. Such hard work can make people dog-tired. And, the situation would be even worse if they became sick as a dog. 
Still, people say every dog has its day. This means that every person enjoys a successful period during his or her life. To be successful, people often have to learn new skills. Yet, some people say that you can never teach an old dog new tricks. They believe that older people do not like to learn new things and will not change the way they do things. 
Some people are compared to dogs in bad ways. People who are unkind or uncaring can be described as meaner than a junkyard dog. Junkyard dogs live in places where people throw away things they do not want. But mean dogs are often used to guard this property. They bark or attack people who try to enter the property. However, sometimes a person who appears to be mean and threatening is really not so bad. We say his bark is worse than his bite. 
Dog expressions also are used to describe the weather. The dog days of summer are the hottest days of the year. A rainstorm may cool the weather. But we do not want it to rain too hard. We do not want it to rain cats and dogs.
A person who lives an unhappy life can be described as “_______”.

A．becoming sick as a dog	B．leading a dog’s life
C．living in a dog-eat-dog world	D．Working like a dog

The underlined word “mean” in Paragraph 4 most probably means “_______”.

A．violent

B．selfish

C．wild

D．Poor

What can we learn from the text?

A．Everyone can be successful if he learns from the old.

B．It might be difficult for the young to learn new skills.

C．Junkyard dogs are careful in money arrangement.

D．Fierce persons aren’t so awful as their appearance sometimes.

To support his idea, the author develops the text mainly by _______.

A．listing reasons	B．using idioms
C．giving examples	D．Making comparisons