Evaluate the results of shi huangdi's effort to standardize weights, measures, and currency.

a. this was an excellent idea that allowed merchants to trade more easily and strengthened the country as a whole.
b. this was a poor idea that failed because it left many merchants feeling like their systems were inferior.
c. this was a good idea that contributed to commerce but isolated the nobles, who often did not know how to read and write.
d. this was a bad idea that prevented many merchants from bartering with those outside their region because they did not understand the new system.