The students assembled in the meeting hall.

Answer: Option C

Assembled : (of people) gather together in one place for a common purpose.
Removed : take (something) away or off from the position occupied.
Diffused : spread over a wide area or between a large number of people.
Dispersed : distribute or spread over a wide area.
Eliminated : completely remove or get rid of (something).

Antonym of Assembled is Dispersed