题目内容：

Howling is a behavior commonly observed among a wolf pack（群）. As pack animals, wolves work together to hunt and rely on howling as an important means of communication among each other. There are different explanations of a wolf’s howl and it appears that there may be more to discover.   

One theory is that wolves howl to bond（结合）better together. It’s almost as if howling together helps the pack stay together, perhaps something similar to people feeling a sense of involvement with each other when singing a song together. But this theory may be wrong, explains Fred H. Harrington, a professor who studies wolf behavior.     Indeed, there have been times when wolves have been seen one moment howling in a chorus, and the next, quarreling among each other. It appears that usually the lowest-ranking members of the pack may actually be “punished” for joining in the chorus at times. So is howling a way to strengthen a social bond or just a way to reconfirm status among its members? —Why do wolves howl for sure?

What is clear, however, is that howling is often used among packmates to locate each other. Hunting grounds are distant and it happens that wolves may separate from one another at times. When this happens, howling appears to be an excellent means of gathering.

Howling, interestingly, is a contagious behavior. When one wolf starts to howl, very likely others will follow. This is often seen to occur in the morning, as if wolves were doing some sort of “roll call” where wolves all howl together to report their presence.

1.What is the possible similarity between wolves’ howling together and human’s singing in chorus?

A. The act of calling each other.

B. The sense of achievement.

C. The act of hunting for something.

D. The sense of belonging to a group.

2.Why does Harrington think the “social bond” theory may be wrong?

A. Wolves separate from each other after howling.

B. Wolves tend to protect their hunting grounds.

C. Wolves sometimes have quarrels after howling together.

D. Wolves of low rank are encouraged to join in the chorus.

3.Researchers are sure that wolves often howl to______.

A. show their ranks

B. find their companions

C. report the missing ones

D. express their loneliness

4.“Howling…is a contagious behaviour” (in the last paragraph) means______.

A. howling is a signal for hunting

B. howling is a way of communication

C. howling often occurs in the morning

D. howling spreads from one to another