You need to identify which long running transactions use an index.
Which dynamic management view should you use?

A.
sys.dm_exec_query_optimizer_info

B.
sys.dm_exec_plan_attributes

C.
sys.dm_exec_requests

D.
sys.dm_exec_procedure_stats

Explanation:
https://docs.microsoft.com/en-us/sql/relational-databases/system-dynamic-management-views/
sys-dm-exec-query-optimizer-info-transact-sql