根据短文内容，从短文后的选项中选出能填入空白处的最佳选项，并将答案写在试卷的答题卷上。选项中有两项为多余选项。
Americans use many expressions with the word “dog”. People in the United States love their dogs and treat them well.      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 existence.
Some people say we live in a dog-eat-dog world.       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.
 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.
   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. 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 are also 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.    .

A．We do not want it to rain cats and dogs.

B．Still, people say every dog has its day.

C．That means many people are competing for the same things, like good jobs.

D．Dogs are their best friends and they are loyal to people.

E. There are many other expressions waiting for you to explore.
F. Some people are compared to dogs in bad ways.
G. They take their dogs for walks, let them play outside and give them good food and medical care.