Consider a multiple regression model examining the impact of various independent variables on the dependent variable Y. The model specified is as follows:
$$ Y = \beta_0 + \beta_1X_1 + \beta_2X_2 + \beta_3X_3 + \epsilon $$
Where:
In the context of this model, which of the following statements is true regarding the assumptions necessary for ordinary least squares (OLS) regression to yield reliable estimates?