Answer: Option C, 1 unit bellow.
Explanation:
The residual of a data point is equal to the vertical distance between the point and the regression line
If the data point is above the line, the residual is positive
if the data point is below the line, the residual is negative.
So here we have a negative residual equal to -1
This would mean that our point is 1 unit below the regression line.
Then the correct option is C.