Test 4, section 4, question #27. Why is the answer D instead of C? Please explain this.

 
The scatterplot shows (my emphasis) “the relative housing cost and the population density for several large US cities in the year 2005.” Note that several is not all, so we can’t use this data to say never. If you plotted all US cities, you very well might see some dots below 61%.

A line of best fit is a predictive tool, but it does not tell you anything definitively.