Choice "D" is correct. If a seller retains a security interest for the sale price of consumer goods, the security interest is automatically perfected; neither filing nor possession by the secured party is necessary. Choice "b" is incorrect. Retention of ownership when the debtor has possession of the collateral is not an effective substitute for obtaining and perfecting a security interest.Choice "c" is incorrect. The security interest is automatically perfected because the computer is a consumer good here (i.e., used for personal purposes as opposed to business purposes).Choice "a" is incorrect. The security interest will be automatically perfected, as explained above.