Answer: the answer should be C. Gillian wanted to host a board game night, but Jackie does not enjoy board games.
Explanation: When creating compound sentences, there are two punctuation rules to keep in mind: 1 Place a comma before the coordinating conjunction. 2 If you're not using a coordinating conjunction, place a semicolon between each clause. As always, you use a lowercase letter to start the second independent clause.
Another example "I really need to go to work, but I am too sick to drive."