Ascientist studied the relationship between the number of trees, x, per acre and number of birds, y, per acre in a neighborhood. she modeled the relationship with a scatter plot and used the equation y= 4 +6x for the regression line. what is the meaning of the slope and y-intercept of this regression line? a. the slope is 6. this means that the average number of birds per acre in an area with no trees is 6. the y-intercept is 4. this means that for every 1 additional tree, she can expect and average of 4 additional birds per acre. b. the slope 4. this means that for every 1 additional tree, she can expect an average of 4 additional birds per acre. the y-intercept is 6. the average number of birds per acre in an area with no trees is 4. c. the slope is 6. this means that for every 1 additional tree, she can expect an average of 6 additional birds per acre. the y-intercept is 4. the average number of birds per acre in an area with no trees is 4. d. the slope is 4. this means that the average number of birds per acre in an area with no trees is 4. the y-intercept is 6. this means that for every 1 additional tree, she can expect an average of 6 additional birds per acre.