Missouri primarily uses which security instrument?

A is incorrect because while mortgages are used in Missouri, they are not the primary security instrument. Mortgages create a direct lien on the property and require judicial foreclosure, which is a more time-consuming process than the non-judicial foreclosure allowed with deeds of trust.

C is incorrect because land contracts (or contracts for deed) are installment sale agreements, not security instruments for loans. They represent a different financing method where the seller retains legal title until the buyer completes payments.

D is incorrect because security agreements are used primarily for personal property (chattel) loans, not real estate. They are governed by Article 9 of the Uniform Commercial Code, which covers secured transactions for movable assets.