According to the web search results1, the timecard_admin role is the minimum role that is required to assign a time sheet policy to a user. A time sheet policy is a rule that controls the creation and operation of time sheets for resources who log time against work items. The timecard_admin role can create and modify time sheet policies, time sheet groups, and time sheet periods, as well as approve time sheets or submit time cards on behalf of team members. The other options are incorrect because:

A. ppm_admin: The ppm_admin role is a higher-level role that can access all Project and Portfolio Management modules and features, but it is not the minimum role required for assigning a time sheet policy to a user2.

C. it_project_manager: The it_project_manager role can create and manage projects, but not assign time sheet policies to users3.

D. It is not possible to assign a time sheet policy to a user: This is false, as it is possible to assign a time sheet policy to a user by using the Time Sheet Policy field on the User form4.

1: 3 2: https://docs.servicenow.com/bundle/vancouver-it-business-management/page/product/project-management/reference/r_Roles.html 3: https://docs.servicenow.com/bundle/vancouver-it-business-management/page/product/project-management/concept/c_ProjectManagement.html 4: https://docs.servicenow.com/bundle/vancouver-it-business-management/page/product/time-card-management/reference/r_TimeCardManagementRoles.html