What is the hold-up problem? Question 8 options: A) It's the problem of downstream firms with market power marking up price above marginal cost, which already has mark-up built into it from upstream firms with market power. B) It's the problem faced by firms choosing to locate in high-crime areas where they are prone to getting robbed. C) It's the problem of firms with market power holding up the price above marginal cost. D) It's the problem faced by firms that are unable to credibly commit to an agreement that involves a sunk investment by their transaction partner, leaving that partner vulnerable to opportunistic behavior