Appends the results of a subsearch to the current results. The append command runs only over historical data and does not produce correct results if used in a real-time search.

Pardon me, C is the correct answer. The append command is used to append the results of one search to another search. It can only be used with a simple search, not a subsearch. The append command accesses historical data, not real-time data.

B is the correct answer.