Ordinary Least Squares Is Used to Estimate a Linear Relationship

Ordinary least squares is used to estimate a linear relationship between a firm's quantity sold per month and its total promotional expenditures, and the slope of the linear function is found to be positive and significantly different from zero. Assuming that all other variables, including product price, were constant during the period covered by the data set, this result implies that

A) the firm should spend more on promotional expenditures.
B) the firm should spend less on promotional expenditures.
C) promotional expenditures influence demand.
D) promotional expenditures have no influence on demand.