The best summary of the information in the excerpt is <em>B. There are many theories about ...</em>
Many theories have attempted to explain the <em>causes</em> of humor among humans. While they are alike, every researcher tends to have an opinion on why humans laugh or smile.
Obviously, humor is triggered by some factors. Studies have also uncovered the importance of humor both for recreational and recovery purposes.
Humor is the grease that lubricates human existence, enabling one to avoid medical and psychological complications arising from our stressful world today.
Humor connects one with others for shared human understanding. And being around people who are humorous increases the ability of one to laugh. Humor eases the stress of life.
Thus, laughter plays an indispensable role in human society and should be encouraged.
