Final answer:
Both FASB and IASB have worked to implement fair value measurement for financial instruments.
Step-by-step explanation:
The correct answer is c. both FASB and IASB.
Both the Financial Accounting Standards Board (FASB) and the International Accounting Standards Board (IASB) have worked to implement fair value measurement for financial instruments.
FASB is the standard-setting body for accounting and financial reporting in the United States, while IASB sets the standards internationally.