What is a flag / option — CCA-F Exam Prep

A forensic detective found 3 files on a suspect's laptop. Then she found 44 more.
Digital forensics case. She ran ls on the desktop folder. Three files: vacation.jpg, notes.txt, budget.xlsx. Looked clean.
Then she ran ls -la. Same folder. 47 files. Hidden configuration files. A .ssh directory with encryption keys. A .bash_history showing every command the suspect ever ran.