C: may be crazy, but also may be normal people trying to adjust to
    unusual social circumstances

    Correct.
Aronson's first law (Aronson Pg. 9) is "People who do crazy things are not necessarily crazy."   This fits closest with the definition given in The Social Animal.  Choice C allows for some people who do crazy things to be crazy, but also allows for some people to do crazy things, and not be crazy (those who are influenced by a "crazy" situation.).