The period is characterized by balance and symmetry. Its antecedent phrase is initiated by a basic idea that recurs at the beginning of the consequent phrase. Unlike the sentence, which exhibits a single cadence, the period contains two cadences, a weak one to end the antecedent and a strong one to end the consequent.
Through the process of elimination, we can remove A and D, since neither of these appears to fit the discus thrower sculptures face. This leaves B and C- and considering the blank, expressionless face the Discus Thrower sculpture has, it is most likely idealistic.