Which of the following methods is best for perfecting an interest in investment property?

To determine the most effective method for perfecting an interest in investment property, it's essential to understand the nuances of how interests in security entitlements, such as investment accounts held with a broker, can be perfected.

The ideal method for perfecting an interest in investment property, particularly in securities or investment accounts, is usually through control agreements with the broker. This is considered the most secure and reliable way to ensure the creditor’s interest is properly established and recognized. Control agreements provide the creditor with the right to direct the broker concerning the investment property, thus granting the creditor a perfected security interest without needing to rely on physical possession or other less reliable methods.

Possession of a paper certificate might apply to certain tangible investments but does not extend to electronically held securities. Similarly, while adding a creditor's name to the account could suggest claims over the property, it does not necessarily offer the level of perfection that a control agreement provides.

The possibility of "best not previously mentioned" might obscure what is considered the most effective method according to the prevailing standards in secured transactions. Control agreements with the broker for investment property stands as the best practice for establishing and safeguarding a creditor's interest.