A customer wants to copy the contents of a previous order to their current order.

To copy the contents of a previous order to a current order, the most appropriate rule type to use is a Data Transform. Data Transforms in Pega are designed to set or copy data from one context to another, making them ideal for this requirement.

B. Data transform: This rule type allows for the manipulation and copying of data between pages, including complex structures such as order contents. It provides a straightforward way to define how data from a previous order should be mapped and copied to the current order, allowing for customizations such as conditionally copying certain items or applying transformations to the data during the copy process.

The other options, such as Data page (A), Declare expression (C), and Function (D), serve different purposes. Data pages are used to load data, Declare expressions for calculating values based on changes in other values, and Functions for executing specific operations, none of which directly address the requirement of copying order contents.