Answer:
B. Loss of earnings from employment
Step-by-step explanation:
David's opportunity cost in this scenario would be the loss of earnings from employment. This is because is no longer employed, meaning that he no longer makes money from his employment due to him "choosing" to quit and start his own business. Therefore, that is the cost of him choosing another opportunity. The financial costs of marketing, taxes, and risk of business failure are all costs he may or may not incur from the chosen opportunity but are not the same as "opportunity costs" since they are costs that need to be met in order to continue this opportunity and not something that was given up in order to choose this opportunity.