Select the abbreviation that tells how the noun clause in quotations is used.
the valedictory prize will be awarded to "whoever has the highest academic rating."
s
op
sc
do

OP. It stands for object of a preposition. An object of a preposition comes after a preposition. In this case, the preposition is "to" and since the noun clause comes after the preposition, it is the object of the preposition.
Hope this helps. 

The answer should be c