An uncomfy Q for the aviators here

You're the First Officer. You notice the Cap'n deviating on something
from the airline's SOP, and it's more important than something like the
taxi speed limit. What do you do?

a) Hope the Cap'n recognizes the deviation on his own;
b) Just pretend you didn't notice it;
c) Get the Cap'n a coffee and gently suggest that you thought
something's a wee amiss; or
d) Tell the Cap'n immediately and emphatically... not recommended, I'd
imagine, considering you'd probably have to work together often after
that too

Presume that there isn't a procedure in the SOP on how to handle
deviations of the Cap'n (kidding)

At least one very experienced pilot has told me that such a scenario
isn't as highly improbable as I'd first imagined

Cheers,

Ramapriya