Answer:
For
Step-by-step explanation:
The phrase for is the most suitable for this sentence is as it is used to describe a period of time. The means that the description is only referring to the last five minutes and not any time before or after.
If we were to put the phrase since into the answer it would be wrong as since is used for an event that has happened in the past and it still continuing. In the question we are only told that the students had only been making noise for the last five minutes.
Hope this helps, have a lovely day! :)