Explanation
Relationship Disclosure Information (RDI) is a document that provides important information about the nature and scope of the relationship between a registered firm and its clients. It covers topics such as the products and services offered by the firm, the fees and charges applicable to the client's account, the risks associated with investing, the conflict of interest management policies of the firm, and the dispute resolution services available to the client. According to Section 14.2 of National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations (NI 31-103), registered firms must provide RDI to their clients before they purchase or sell securities for them or advise them to do so. Registered firms must also update RDI in a timely manner if there are any significant changes to it. To evidence that they have satisfied their RDI obligation, registered firms may retain a copy of the RDI in the client file with detailed notes to confirm that they have provided and explained RDI to their clients. This is one of the acceptable methods suggested by Alberta Securities Commission (ASC) in its presentation on RDI1. Delivering RDI only upon request or using a letter of engagement are not sufficient methods to comply with NI 31-103. Providing and explaining Fund Facts is a separate obligation under NI 31-101 Mutual Fund Distribution Rules.
References: Relationship Disclosure Information August 2021, Relationship Disclosure Information, Relationship Disclosure Information

Explanation
A Canadian equity index fund is a type of mutual fund that invests in a portfolio of stocks that track the performance of a Canadian stock market index, such as the S&P/TSX Composite Index. This fund would be the most tax-efficient option for Xerxes, because it has low turnover and generates mostly capital gains, which are taxed at a lower rate than interest income or dividends. A bond fund would generate interest income, which is taxed at the highest marginal rate. An asset allocation fund would have a mix of different types of investments, which may not be optimal for Xerxes' tax situation. A target date fund would adjust its asset mix over time based on a predetermined retirement date, which may not match Xerxes' goals or risk tolerance.
(Canadian Investment Funds Course, Chapter 9, Section 9.2)
References:
Canadian Investment Funds Course, Chapter 9, Section 9.2: Tax-Efficient Investing IFSE Institute: Tax-Efficient Investing1 Investopedia: Tax-Efficient Investing2