15. The following statement about correlation coefficient is true: I. The correlation coefficient and the slope of the regression line may have opposite signs. II. A correlation of 1 indicates a perfect cause-and-effect relationship between the variables. III. Correlations of +.87 and −.87 indicate the same degree of clustering around the regression line. (A) I only (B) II only (C) III only (D) I and II (E) I, II, and III