An investment adviser must notify clients of which necessary details regarding custody of their assets?

The duty of an investment adviser regarding custody of client assets includes providing clear information to clients about who is holding their assets. This information specifically includes the name and address of the custodian responsible for the assets, as well as a notice indicating that the adviser has custody of the client's funds or securities.

This requirement is crucial because it ensures transparency and helps clients verify that their assets are being held securely and by a reputable entity. It also allows clients to independently contact the custodian if they have inquiries or concerns about their investments.

While the other options include relevant aspects of investment management, they do not encompass the specific legal requirements related to custody notification. For instance, the estimated value of the assets, risks involved, or trading costs may be important for overall investment strategy, but those details do not directly address the custodial requirements. Similarly, while frequency of statements and security measures are significant, they fall under different areas of compliance and client responsibility.