C: that Nancy's attitude cannot be inferred
from the essay on account
of the conditions under which it was
written
Incorrect.
Research on the fundamental attribution error has shown,
that even when people have reason to believe that the causes for a behavior
are situational, they still overestimate dispositional factors. Since
choice C calls for the professor to give a lot of credence to the situation
that was at hand, it contradicts research on the fundamental attribution
error. The professor would probably believe that Nancy actually believed
what she wrote.