If all the points in a scatter diagram lie on the least squares regression line, then the coefficient of correlation must be:
A. 1
B. either 1 or -1
C. -1
D. 0

If the coefficient of correlation is -0.80, the percentage of the variation in y that is explained by the variation in x is:
A. 64%
B. -64%
C. 80%
D. -80%