Credit risk - options

I understand that the buyer always bears a potential credit risk, because the seller would owe the payoff if in the money option is exercised… now… why is it that the option buyer currently bears the market value of the call? (ref: 2010 cfai mock exam)

is it because MV(call) represents a potential payoff of the option? hmm… i guess in this case it makes sense… (i answered my own question…)