Identifying organization wide common controls is the correct option.

This activity is carried out at the enterprise tier because the Prepare step at the organizational level establishes governance and controls that apply across multiple systems. Identifying organization wide common controls means selecting and documenting controls that individual systems can inherit to ensure consistent security and to reduce duplicated effort across the enterprise.

Listing stakeholders for a specific system is incorrect because identifying stakeholders is a system level task that focuses on owners, users, and other parties relevant to a particular system rather than enterprise wide controls.

Establishing a system security baseline is incorrect because security baselines are tailored to individual system configurations and are typically set at the system tier during system implementation and configuration activities.

Compiling an inventory of assets is incorrect because maintaining asset inventories is an operational or system level activity and while it supports enterprise risk management it is not the enterprise Prepare activity that defines common controls.

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