The scatterplot shows the relationship between the number of hours studied, , and the test score, . Which of the following graphs shows the most appropriate model for the data? (Assume the scatterplot  now displays points that generally increase linearly from left to right, with a positive slope.)
A graph showing a straight line with a positive slope that passes through the middle of the linearly increasing data points. 
A graph showing a straight line with a negative slope. 
A graph showing a curved line. 
A graph showing a horizontal line. 