Hello there!
Your answer would be C). Opportunity cost
The reason is why this would be your answer is because an opportunity cost is the value of an offer that an individual or a group of people had to give up in order to get a better offer. This happens all the time because there are people that get multiple offers, but then they would have to choose the best one that they want to take on, and would need to leave another offer as the "second-best." This would be known as the second option that would be the next runner up after the offer that was made.
Lets give you an example:
Tracie got two offers from a cleaning business that wants to invest in cleaning her donut company.
Offer #1 offers to charge her $25 a month for cleaning services.
Offer #2 offers to charge her $20 a month for cleaning services.
Tracie would choose Offer #2 because it is a cheaper service, therefore leaving the 1st offer as an opportunity cost, since she didn't take the offer but it is her 2nd best option.