Traders were part of the class.
a. noble
c. lower
b. upper
d. middle

Depending on the time period, the social class of traders changed.

If you are talking about Medieval to Early Renaissance, I would say your answer is C because traders were looked down upon and considered vagrants.

However if you are talking about High Renaissance onward you would see improvements in the standings of traders, rising to middle, possible even upper. So if the time period your problem is stating is of the High Renaissance onward I would say B or D.