What are the authorized code letters for a rectangular Drop Zone (DZ)?

The authorized code letters for a rectangular Drop Zone (DZ) are indeed classified under a specific set of conventions, ensuring standardization and clear communication among military personnel. The option that includes "JCARS" stands for Joint Contingency Operations Reference System, which is a recognized code in military operations used to designate Drop Zones in a way that can be understood universally by those following established protocols.

In contrast, other choices either do not follow the established coding system for DZs or do not represent recognized acronyms related to Drop Zone designation. Each of these alternatives lacks the authorization or familiarity within the contexts of military parachuting and logistics that "JCARS" holds, making this choice the correct one for designating a rectangular Drop Zone effectively and clearly in operational planning and execution.