Which of the following is a shortfall of international diversification? Select one: a. Emerging market returns exhibit positive serial correlation through time. b. Correlations between the returns of international portfolios are most positive with each other in bad economic times. c. International markets are less than perfectly positively correlated. d. Emerging market returns exhibit negative serial correlation through time. e. Correlations between the returns of international portfolios are most positive with each other in good economic times.