employment level in the non-agricultural sector

Question 33:
The regression analysis below relates the value of new car sales (in millions of dollars) and the independent variables “compensation” (in billions of dollars) and “employment level in the non-agricultural sector” (in thousands) for 44 consecutive quarters.

The coefficient for employment level, 0.21, describes:

Car Sales Multiple Regression Source

The behavior of car sales as the employments level changes, controlling for compensation. The behavior of the employment level as car sales change, not controlling for compensation. The behavior of car sales as the employment level changes, not controlling for compensation. The behavior of the employment level as car sales change, controlling for compensation.