Which of the following is not a requirement of becoming a house representative?
a. must be at least 25 years old
b. must have at least a college degree
c. must have been a citizen for 7 years
d. must live in the state he or she represents

There is no requirement  for the education that a representative must have: people who will vote for them will judge whether the education is enough. This allows people who could not afford education, but are otherwise competent to win.
The correct answer is then B.

All the other options are requirements: the age, citizenship and residence.