Answer: C. Cosima didn't want to stop at the store on her way home from work, but she knew she needed cat food.
Step-by-step explanation: a conjunction is a word that has the function to connect two or more clauses or sentences. A coordinating conjunction is a conjunction placed between words, phrases, clauses, or sentences of equal rank. From the given options, the one that contains an example of the use of a coordinating conjunction to explain how ideas are related in terms of contrast or opposition is the sentence corresponding to option C, with the coordinating conjunction "but."