B is correct because assessing historical differences in the rate of return per unit of risk of similar mutual funds helps a Dealing Representative to compare the performance and risk-adjusted returns of different mutual funds and select the most suitable one for a client's risk tolerance and investment objectives.
Comparing historical rates of return between different types of mutual funds (A) does not account for the risk involved in each type of fund. Referencing the fund code for each mutual fund that is being compared does not provide any information about the fund's characteristics, features, or suitability. The rights a client has if there is a desire to cancel the purchased mutual fund (D) are not relevant for determining a suitable mutual fund for a client.