When can an assignee decline a task if an option is enabled for a step? 

Answer options:

A. if there are multiple assignees on the step and the others have all already declined
B. if the assignee is the only assignee on the step and has the ability to add assignees on the step
C. if the assignee is the only assignee on the step and has the ability to add CC
D. if there are multiple assignees on the step who are yet to accept/decline the task

D

Reference: http://docs.oracle.com/cd/E75748_01/English/User_Guides/user/helpmain.htm?toc.htm?73279.htm