C because it's the most detailed explanation and answer. It goes over beginning middle and end
I would say this would classify as a downward comparison as the person is talking about Mark who has a poorer job situation than him and this could be used to bolster the speaker's ego or to knock poor Mark or could just be an observation.
Hey there!
The present tense would be swim.
This is because it suggests your swimming in the present, instead of swum or swam, which suggests that you did these 50 laps in the past.
Hope this helps!
