AWS Certified SysOps Administrator - Associate SOA-C02 — Question 15

A company recently acquired another corporation and all of that corporation's AWS accounts. A financial analyst needs the cost data from these accounts. A SysOps administrator uses Cost Explorer to generate cost and usage reports. The SysOps administrator notices that "No Tagkey" represents 20% of the monthly cost. What should the SysOps administrator do to tag the "No Tagkey" resources?