A Negative Covariance Between the Returns of Stock a and Stock

A negative covariance between the returns of Stock A and Stock B indicates that

A) market prices of Stock A and Stock B move in tandem when their returns are declining.
B) the return on one stock will exceed that stock's average return when the second stock has a return that is less than its average.
C) a portfolio investing equally in Stocks A and B will have a negative expected rate of return.
D) both Stock A and Stock B have negative rates of return for the period.
E) one stock has a negative rate of return while the other stock has a positive rate of return for the period.