:4. A scatter diagram contains five points. Four of them lie on
a straight line. The fifth one does not lie on that line. Let r
be the correlation coefficient of the scatter diagram. One of
the following is true. Which one?

a. Since 80% of the points lie on a straight line, r has to
equal 0.8 or -0.8.

b. r has to equal -1

c. r has to equal 1

d. r is either 1 or -1, but we can't tell which.

e. r doesn't need to be 0.8 or -0.8, but it certainly is
neither 1 nor -1.