John and Jim are both risk averse and only care about the mean and standard deviation of their portfolio's return. They agree on the opportunity set available. There are N risky assets and a riskless asset. Which of the following statements is correct?

A. John and Jim hold the same portfolio of all assets.

B. John and Jim may hold completely different portfolios of risky assets.

C. When choosing between 2 portfolios, John and Jim always prefer the one with the lowest standard deviation.

D. John holds any two risky assets in the same ratio as Jim does in the portfolio.