Residuals describes how far each point is from the regression model. The, the farther each point is from the line, the worse the fit is and the closer each point is to the regression line, the better the fit.
From the given picture, we can to see that graph B has point that are not tightly centered around the lines. So this is not a good fit. Similarly, graph A has a u-shape and the points are not tightly centered around the line then it is not a good fit.
However, graph C shows that all points are tightly centered around the line, so this is a good fit. The, the answer is option C: Data set C