Final answer:
The Investment Industry Association of Canada (IIAC) is the best organization for ARC Investments to present arguments against federal government legislation, as IIAC focuses on advocacy and public policy issues for the investment industry.
Step-by-step explanation:
If ARC Investments is unhappy about legislation that the federal government is considering, the best entity to approach to present arguments against the legislation would likely be the Investment Industry Association of Canada (IIAC). The IIAC represents the investment industry's interests and is a standard advocate for regulatory and public policy issues on behalf of its members. They would be the most appropriate body for discussing concerns about proposed legislation, as they engage in lobbying and advocacy work with government officials and policymakers. On the other hand, bodies like the Investment Industry Regulatory Organization of Canada (IIROC) oversee the conduct of its member firms and their registered employees, the Ombudsman for Banking Services and Investments (OBSI) provides consumers and small businesses with an alternative dispute resolution service, and the Canadian Investor Protection Fund (CIPF) protects investors in case of the insolvency of a member firm.