Which sentence uses the word "than" or "then" in a way that is often contested or identified as "wrong"?

Responses
A If you are so good at fixing broken appliances, then why don't you fix the leaky refrigerator?If you are so good at fixing broken appliances, then why don't you fix the leaky refrigerator?
B Rather than argue over the definitions of certain words, let's just agree to table this discussion.Rather than argue over the definitions of certain words, let's just agree to table this discussion.
C At first, I was unsure about going to the gym, than I went for a few days and found out I loved it!At first, I was unsure about going to the gym, than I went for a few days and found out I loved it!
D When Margaret told me that she was the only one going to the dance, I said, "I"m not sure I'm going then."

C At first, I was unsure about going to the gym, than I went for a few days and found out I loved it!