Which of the following is a correct description of how the returns on assets move together? A. Positive and negative deviations between assets at similar times give a negative covariance. B. Positive and negative deviations between assets at dissimilar times give a negative covariance. C. Positive and negative deviations between assets give a zero covariance. D. Positive and negative deviations between assets at dissimilar times give a positive covariance