@SeniorPatzer could Radjabov appeal and demand his rightful chance as a Candidate to contest for the Challenger's seat in the World Championship?
If that is the case, then actually option B would be correct. after all, he EARNED his spot as a Candidate.
but let's take the "what if" a step further. Given the fact that the Wuhan virus has resulted in quite a few fatalities; and given the fact that one does not become symptomatic until days after the virus is contracted; It is very likely that if one person gets it, they will all get it. and if they all get it, then they are all at risk of dying from it.
So, what if all 8 Candidates die from the Wuhan virus? Would that convince FIDE to allow Radjabov to play Carlsen for the title?
Actually, I think there's another possibility. Restart the entire Candidates 2020 from scratch, and have a 9-player Double Round-Robin instead! Include BOTH Radjabov and MVL.
With regards to your last hypothetical, I don't think that will happen. It's extremely improbable given the statistical data that's been collected so far.
Here's a slightly more likely scenario than the one you pose. Suppose Nepo transmitted the Wuhan/Covid-19 virus to Ding during their Round 6. That would totally suck for Ding. "I lose the game to Nepo AND I get infected by Nepo!!! What the $%#! I left China, stayed in quarantine for 14 days in Russia, and then I get infected in Russia??!"
I don't think Ding and the Chinese chess federation would be pleased.
Nepo might have the common cold instead of SARS-cov2.
Yesterday, I had a conversation with Emil Sutovsky and some others. He defended the decision to continue the tournament, but agreed the opening ceremony could have had a smaller reception. He seemed to suggest that was the responsibility of the city's organizers who wanted a big crowd. At least FIDE kept the eight contestants away from that. He did not commit at that time to cancelling the closing ceremony.
The situation is changing so rapidly though that it's entirely possible the tournament could get cancelled. Emil Sutovsky said that cancelling the tournament would not only be a major blow to FIDE (whose main revenue source is the World Championship), but to all of chess. He may be right.
But I think it's becoming more likely that the event will be cancelled. Ding Liren, who went more than 100 games without defeat, has lost three of his first six games. If Grischuk falls significantly off the pace, he may withdraw anyway. And that's all presuming that the eight players are physically healthy. The mental strain of the virus is clearly affecting the players.