Which sentence uses a comma and a coordinating conjunction correctly to separate two independent clauses?

A. To be honest, I always thought you'd be better at playing goalie.
B. Staying alert, and making good decisions are part of being a responsible babysitter.
C. It looks as if it might rain, so I brought two umbrellas for us to use.
D. We can do our homework together or, you can just come over when you're done.