Question

which detail explains the challenging part of an escape room?
there is a file of notes.
there are hidden clues.
there are many themes.
there is plenty of time.

Explanation:

Escape rooms are challenging because participants must find and interpret clues to progress. Hidden clues require effort to locate, creating the core challenge. Other options either do not create difficulty (plenty of time, file of notes) or are just a feature (many themes).

Answer:

There are hidden clues.