With data labeling, the data owner must be the key decision maker. The data owner is the person or entity that has the authority and responsibility for the data, including its classification, protection, and usage. The data owner must decide how to label the data according to its sensitivity, criticality, and value, and communicate the labeling scheme to the data custodians and users. The data owner must also review and update the data labels as needed. The other options are not the key decision makers for data labeling, as they either do not have the authority or responsibility for the data (A, B, and C), or do not have the knowledge or interest in the data (B and C). References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 2, page 63; Official (ISC)2 CISSP CBK Reference, Fifth Edition, Chapter 2, page 69.