Final answer:
Permissions can be assigned at different levels in Azure, and Admin1 can reduce permissions on VM1 by removing the redundant Owner role from User4 or User3, or the Reader role from User3.
Step-by-step explanation:
The question pertains to the management of access permissions within Microsoft Azure, specifically regarding a virtual machine and the roles assigned to different users. In Azure, permissions can be assigned at various levels, such as the subscription level, resource group level, and the resource level.
User1 has the Reader role at the subscription level for Sub1, which allows the user to view but not make any changes. User2 has the Owner role on the resource group RG1, giving them full management rights over it. User3 has been given the Reader role specifically on VM1, allowing them to view the virtual machine properties. Lastly, User4 has the Owner role on VM1 as well, granting full management rights over the virtual machine.
Considering another administrator, Admin1, wants to reduce permissions on VM1: since having two owners could be redundant, Admin1 could remove either User4's or User3's Owner role without affecting the overall administrative capabilities on the virtual machine. Removing the Reader role for User3 could also be considered if deemed necessary to reduce permissions further.