Which sentence below contains a correctly used modifier in italicsa) joe looked sad at his broken bikeb) the sauce tasted bitterly & i couldn't swallow it.
c. he spoke sharply to his sisterd) i feel goodly now that i am over the flu.?

The correct answer should be C, he spoke sharply to his sister. 

In sentence A, sad should be sadly. 

In sentence B, bitterly should be bitter. 

In sentence D, goodly should be good. But I'd say that it would sound better if the sentence is, "I feel better now that I am over the flu."