To determine which pair of points should be used to find the line of best-fit for the scatterplot, you typically want to select points that best represent the overall trend of the data. The option "K and M" suggests that these points align with the trend line of the scatterplot.
Without the actual visual of the scatterplot to analyze, we should go with the choice that indicates consistency with the trend if "K and M" is mentioned as a pair through which a trend line would go.
Thus, the pair of points that should be used to find the line of best-fit for the scatterplot is K and M.