Final answer:
The most effective method for perfecting a security interest in investment property is obtaining control over the property, as it provides the secured party with the highest level of priority over other claimants.
Step-by-step explanation:
The best method to perfect a security interest when dealing with investment property is 3) Obtaining control over the property. Filing a financing statement may put the public on notice of the security interest, but control is typically the strongest and most definitive means of perfecting a security interest in investment property. Having control means that the secured party has taken necessary steps, as defined by the Uniform Commercial Code (UCC), to ensure that they have priority over other creditors in the event of default. This can involve having the investment property registered in the name of the secured party, entering into a control agreement with the intermediary (such as a broker-dealer or securities intermediary), or taking other legal steps to ensure that the secured party can direct the disposition of the securities without further consent of the debtor.