Final answer:
The agency that handles trade practice complaints regarding violations of the Conduct Rules is the Financial Industry Regulatory Authority (FINRA).
Step-by-step explanation:
The agency that handles trade practice complaints regarding violations of the Conduct Rules is the Financial Industry Regulatory Authority (FINRA). FINRA is a self-regulatory organization (SRO) that regulates and supervises the sale of securities and the brokers, dealers, and bankers who sell them. It aims to protect investors and ensure fair and ethical practices in the securities industry.