[Copernicus]

Since its only half of your chips and its the first hand, there will be later rounds of betting on this hand, so I would think the answer is between A and B if you dont know his hand precisely, just the % you are favored. (If it were C D or E you would reraise the rest of the stack, since you now have some folding equity that you didnt have in the first question, where *less* than 60% was sufficient). If a lot of the value in the winning % isnt likely to develop until the turn or river, and there could be pressure to fold on the flop than I think you have to tighten up to answer B and make your best judgement on the flop. If its a hand thats ahead from the start then I would go with A because you have some folding equity on the flop.

If he has flashed his cards as in the first question, knowing his exact hand would enable a precise calculation on the flop which is enough of an edge to make A right pre-flop IMO.