Question 12 (2 marks) Which of the following statements is most correct? a. Sunk costs must be included in a project's cash flow. b. Research and development expenditures cannot be a part of the initial cost of a project. c. Opportunity costs are sunk costs, so they should not be included in the cost of a project. d. Depreciation is not a cash expense. O a. O b. O c. Od.