Answer:
I think the answer would be C.
Step-by-step explanation:
First off, the answer A doesn't even make any grammatical sense. Answer B while does fit in to the sentence, doesn't contribute anything to the outcome of the cake. It isn't even an adjective. D could possibly be the right answer, but the sentence made sure to force the amount of work needed to create the cake, and "disappointing tragic" just doesn't seem right in that situation. Therefore, the answer should be C.