We study mythology. what should the writer add to the end of the sentence in order to create a complex sentence
a. in the morning before english and science.
b. but we also study math and geography.
c. if we have free time in the afternoon.
d. and we learn the history of ancient greece.

If you're on edgenuity I am positive that the answer is C. Because A complex sentence joins an independent clause with one or more dependent clauses, and in this case, we have one dependent clause in "if we have free time in the afternoon" the word "If" makes the second part dependent, whereas "We study mythology" is independent. 

Ithink that story needs some revising. hmm some academic language perhaps? and sylvia is but i do think that rainbow is spectacular