Who is an Investment Advisor?

Which of the following individuals need to register with the SEC under the Investment Advisers Act of 1940?
- Adam who retired last year from a big brokerage house but he recently started providing services to 12 clients who live in his neighborhood that he met while out golfing.
- Belinda who writes weekly investment articles for a local newspaper.
- Carter who provides incidental services as an accountant.
- Diane who provides investment services only to three large insurance companies