Which of the Following Statements About GDP Is Correct

Which of the following statements about GDP is correct?

A) GDP measures two things at once: the total income of everyone in the economy and the total expenditure on the economy's output of goods and services.
B) Money continuously flows from households to firms and then back to households,and GDP measures this flow of money.
C) GDP is generally regarded as the best single measure of a society's economic well-being.
D) All of the above are correct.