Genetics and training only takes you up to the physical potential. That's a given in bike-racing because everyone else at the top-levels has gone through roughly the same training. However, to succeed in bike-racing you've got to have a brain that's fast, nimble, flexible and learns quickly. Not sure if there's a way to test or predict that. I would say that someone's who good at chess might have the type of strategic mindset that's helpful in bike-racing. I've known plenty of guys that can drop me on every single training-ride; they'd be first up every single hill, get the fastest TT times, ride the farthest and fastest. Yet in a race, they're nowhere to be found at the end, either OTB or stuck in the pack somewhere.

There's something that I've never been able to quantify and express clearly. That's how to "read" people. Like scanning people in a club/bar and being able to figure out instantly which ones are most receptive to an approach and being able to customize a greeting that'll have the most success. It's something that you "feel" , partly through practice and partly through intuition and instinct. Same thing in a race, you can look around the pack and pick out quickly who you need to follow around because they're gonna be finishing 2nd (after you). You can also pick out the ones who are weak or likely crash candidates. I'm just not sure how to get this aspect across in words, it's something you pick up through non-verbal body-language.

At the amateur enthusiast levels that we're at here on this board, I doubt physical genetic potential has much to do with our relative performances. Unless you're actually competing in the TDF/Olympics or are a Pro where your paycheck depends on it, none of us are at the limits of our genetic potential. Such that we can compare our performance to someone elses and attribute the differences to genetics. By far, most of the differences will be the mental intellectual aspects. Learning how to ride, learning how to develop an effective training-programme to get maximum performance increases, being able to stick to it day-after-day, week-to-week, months and years on end, quickly learning pack-tactics, reacting nimbly and developing pack-strategies on the fly are probably the biggest determining factors in our successes (or lack thereof).

I vote for C) Through training, time will tell.