C would be correct if "both" were omitted.
All the other sentences have errors, too.
Which sentence has correct subject - verb agreement
a) casey or robbie are coming to the movies with us
b) swimming and skiing is my favorite sports
c) sandwhiches or pizza both sounds good for a quick dinner**
d) either your brother or his friend is making a lot of noise upstairs
3 answers
I think that D is correct. The either-or-construction takes a singular verb.
What is the answer please