The sentence "Brandy and LaTina's favorite singer were coming to town that weekend." contains a subject-verb agreement error because the subject "singer" is singular. The correct option to fix the sentence is:
C. Change were to came.
The corrected sentence would read: "Brandy and LaTina's favorite singer came to town that weekend."
(Note: While option C is the correct choice to resolve the issue of agreement in tense, a more straightforward correction for subject-verb agreement would technically involve changing "were" to "was" instead, which is not one of the provided options.)