An economist is developing a regression model of real GDP as a function of labor input. She needs to select a time series that represents the total amount of labor performed in a year. Which of the following is the most appropriate indicator of total labor performed that she can use for this model（）
A. Aggregate hours.
B. Average workweek.
C. Number of employed.
参考答案：A
解析：
Aggregate hours measures the total number of hours worked in a year by all employed people. Aggregate hours takes account of both the level of employment and the average workweek, making it superior to either of those measures as an indicator of total labor performed. Total labor compensation is a measure of real wage rates that includes wages, salaries, and employer-paid benefits.