Which technique (s) does Shakespeare use to speed the pace of Hamlet in Act IV?

fewer scenes

more fighting

shorter length

more settings

In my opinion, the correct answer is D. More settings.

Act IV happens in various places: in the royal chambers, where Gertrude talks to Claudius and tells him of Hamlet's murder; at the hall, where Claudius communicates with Rosenkrantz and Guildenstern. Then the two of them meet Hamlet, in the juicy Scene 2. After that, the setting changes to Danish coast, where Hamlet prepares to depart from Denmark, and sees Fortinbras. A few days later, we are on the court again, seeing mad Ophelia. The next scene happens on the graveyard. So, this act presents us with few different places, and it happens in the course of few weeks.

As for other options, they are not correct because:

A. This act has actually more scenes than any other.

B. There isn't any fighting, except for the conflict between Hamlet and Laertes.

C. It isn't shorter than other scenes. On the contrary, it is quite long.