The document that is owned by executive management and sets the purpose of BCM in an organization is the Business Continuity Policy. The Business Continuity Policy is a high-level document that defines the scope, objectives, principles, and roles and responsibilities for business continuity management within the organization. It also demonstrates the commitment of top management to support and continually improve the BCMS. The Business Continuity Policy is one of the mandatory documents required by ISO 22301, the international standard for BCMS12.

The other options are not correct because they are not documents that are owned by executive management and set the purpose of BCM in an organization. A Business Process Policy is a document that describes the procedures and rules for performing a specific business process, such as procurement, sales, or accounting. A Register is a document that records and tracks the status of certain items, such as risks, incidents, or assets. A Worksheet is a document that contains data and calculations, such as a spreadsheet or a form.

References: 1: ISO 22301:2019, Security and resilience — Business continuity management systems — Requirements, 5.3 2: ISO 22301 Auditing eBook, Chapter 2.2.2