Which sentence correctly combines a modal verb and a contrastive conjunction?

A. We must leave for the airport early to catch our flight, yet we might still miss it due to traffic.

B. He might attend the concert tonight, but he must finish his assignment first.

C. She should go to the gym regularly, or she might not see any progress in her fitness goals.

D. They could go to the concert this weekend, yet they could also go to the theater instead.