A multiple regression model has the form: y = 2 + 3×1 + 4×2. As x1 increases by 1 unit (holding x2 constant), y will

The correct answer is A.

The multiple regression model has the form: $y = 2 + 3x_1 + 4x_2$. This means that the dependent variable $y$ is predicted to be 2 units when $x_1$ and $x_2$ are both 0, and it is predicted to increase by 3 units for every unit increase in $x_1$, holding $x_2$ constant. Similarly, it is predicted to increase by 4 units for every unit increase in $x_2$, holding $x_1$ constant.

Therefore, if $x_1$ increases by 1 unit, holding $x_2$ constant, $y$ is predicted to increase by 3 units.