According to the CRISC Review Manual, risk taxonomy is the system of classification and categorization of risks based on common characteristics and attributes. Risk taxonomy is necessary to enable an IT risk register to be consolidated with the rest of the organization’s risk register, because it helps to ensure consistency, comparability, and alignment of the risks across the organization. Risk taxonomy also helps to facilitate the communication, reporting, and aggregation of the risks. The other options are not the correct answers, because they are not essential for consolidating the risk registers. Risk response is the action taken to address the risk, which may vary depending on the risk level and strategy. Risk appetite is the amount and type of risk that an organization is willing to accept, which may differ across the organization’s units and functions. Risk ranking is the process of prioritizing the risks based on their impact and likelihood, which may change over time and context. References = CRISC Review Manual, 7th Edition, Chapter 2, Section 2.1.2, page 69.