:6. Consider diagram ? on page ? of the test. It shows a
scatter diagram, its approximate regression line, and four
vertical line segments marked A,B,C, and D. Each of these line
segments represents an error (where by the "error" of a point is
meant its distance from the regression line).  One of these
errors is about the size of the rms error of th regression line. 
Which one? <p>

a.  A <p>

b.  B <p>

c.  C <p>

d.  D