单选题 A portfolio currently holds Randy Co. and the portfolio manager is thinking of adding either XYZ Co. or Branton Co. to the portfolio. All three stocks offer the same expected return and total risk. The covariance of returns between Randy Co. and XYZ is + 0.5 and the covariance between Randy Co. and Branton Co. is- 0.5. The portfolio's risk would decrease: A. most if she put half your money in XYZ Co. and half in Branton Co. B. more if she bought Branton Co. C. if she bought XYZ Co. but increase if she bought Branton Co.

【正确答案】 B

【答案解析】In portfolio composition questions, return and standard deviation are the key variables. Here you are told that both returns and standard deviations are equal. Thus, you just want to pick the companies with the lowest covariance, because that would mean you picked the ones with the lowest correlation coefficient.