And you can use the other possibilities, in other contexts: 'Do you keep your car in a garage?'/'No - on the street outside my house.' But in this case 'on the road' means 'in service - perhaps on a road, perhaps on a motorway, even 'off-road' - possibly.
Cambridge Dictionaries Online - Cambridge University Press) in every other way, but they 'deny its existence' - which you wouldn't expect a sophisticated person to do.
As to b and c: 'potentially' would mean, 'they could have been sophisticated, but this failure prevents it'. It is just possible, but a is better. c also is just possible; it would mean 'they are trying to pretend that they're sophisticated - they hope that people will think it - but this failure makes the disguise imperfect'. Again, a is better.