Respuesta :
The second sentence, "I love vanilla ice cream, but my sister likes butter pecan," has the correct punctuation. In a compound sentence, the comma always goes before the coordinating conjunction (In your case, this conjunction was "but.").
Answer: I love vanilla ice cream, but my sister likes butter pecan.
Explanation: You can use a comma before the coordinating conjunction "but," but not after; the first option is therefore ruled out; however, when using the conjunctive adverb "however" to join two independent clauses, a semicolon should precede it and a comma should follow it (that is why neither the fourth nor the third options are correct).