Fund managers and fund custodians who participate in fund operation only charge management fees and custody fees according to the agreed proportion, and have no right to participate in fund income distribution or bear fund investment risks. Option a is wrong. Systemic risk affects all securities in the capital market, which is also called undivided risk. Systemic risk cannot be reduced with the increase of asset types, and item B is correct; Non-systematic risk, also known as distributable risk, can decrease with the increase of asset types, and option C is correct; Changes in national economic policies are systemic risks, and option D is correct.