A would be the go-to option and is quite predictable, but not unwelcome and would probably lead to sexy times.
B, on the other hand, opens up a whole other can of worms. A flustered, shy Mari would be super cute, and just imagine how Kanan would feel about that. She's probably be like, "I...I never knew Mari could be this cute..." and then sexy times with flustered, shy Mari ensues.
^I still don't know why people bring up the source material considering KyoAni already diverged from it in a significant way when it came to some of the relationships. Contrary to what people posit, adaptations can definitely stray from the source material if they want to. Adaptations are standalone, at least insofar as canon is concerned.