阅读下列四篇短文，从每小题后所给的A,B,C或D四个选项中，选出最佳选项。
Howling is a behaviour commonly observed among a wolf pack. 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 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 behaviour.
