Answer & Explanation
D) Remove the TABLOCK option from the BULK INSERT statement.
The TABLOCK hint increases the number of locks during the adding process. This is the reason why response time are slows down during this process. By removing the TABLOCK hint the default more granular row-level lock will be used. This would decrease the scope of the locks which would result in less waiting jobs and performance would improve.
Note: The BULK INSERT statement is used to copy a data file into a database table or view in a format specified by the user. The BULK INSERT statement accepts the TABLOCK hint, which allows the user to specify the locking behavior that the BULK INSERT statement should use. TABLOCK specifies that a bulk update table-level lock is taken for the duration of the bulk copy. If TABLOCK is not specified, the default uses row-level locks.