You manage a SQL Server 2014 instance that contains a database named DB1.
Users report that some queries to DB1 take longer than expected. Although most queries run in less than one
second, some queries take up to 20 seconds to run.
You need to view all of the performance statistics for each database file.
Which method should you use?

A.
Query the sys.dm_os_tasks dynamic management view.

B.
Query the sys.dm_os_performance_counters dynamic management view.

C.
Query the sys.dm_io_virtual_file_stats dynamic management function.

D.
Examine the Data File I/O pane in Activity Monitor.

Explanation:
sys.dm_io_virtual_file_stats
Returns I/O statistics for data and log files.
sys.dm_io_virtual_file_stats (Transact-SQL)