Managers Want to Ensure That Every Issue in Jira Always

Managers want to ensure that every issue in Jira always has an assignee. Which change will definitely meet this requirement?

A) Update post functions to set the assignee appropriately at each workflow transition.
B) Set Default Assignee to Project Lead in every project.
C) Use components for automatic assignment in every project.
D) Make the assignee required on workflow transition screens.
E) Make the assignee required through field configurations.
F) Set the global option "Allow unassigned issues" to OFF.