[单选题]Passage two
This is what I have noticed in sports club: In every class at my club, every single attendee is female. They are old, they are young; some are fit, and some are not. But, save for one of the instructors, they are all women. Conversely, just about every man in the club (including me) works out by himself, usually on the machines or free weights.
This is not something accidental. As it relates to the sexes, there must be some insights into human behavior. But what? Could it be that women feel more comfortable in groups than men? If so, why? And in what way do men feel more comfortable? Why do we prefer exercising alone?
Digging deeper, I wonder if these distinctive behaviors are markers for both genders. Men have always identified with the lone wolf. Look at the heroes in the movies. We have the Marlboro Man, even the Terminator. Men find something timeless and appealing to the lonely heroes, always. Clint Eastwood and Rambo acted alone. The darker the persona (角色) the more men relate. They become heroes when they save others and solve serious problems – all by themselves. Necessarily, then, this would have women identifying with groups, like The Real Housewives of …
However, men also play on teams. We can relate to a band of brothers and fight on battlefields together. So, why is it that women almost universally work out in groups and men don’t?
I believe it has more to do with each gender’s willingness to ask for help. In other words, the same psychology that makes so many men reluctant to ask for directions is also what keeps them out of those gym classes. Ironically, it is a defect of character, but the role of problem solver is too deep-rooted in their masculinity for them to behave otherwise. Subconsciously considering themselves capable of solving problems individually, men would regard it feminine to ask for help from others, especially at the gym, where their physical manhood is on display. In general, women don’t have this problem. They take comfort in unity or are at least motivated by that unity. 
 
27.The author mentions some roles in movies for the purpose of ___________.