Four are essential to case study  iteration, OTTR, triangulation, and ruling out rival explanations.
Four are needed for making sure the rival explanations are ruled out.
Four are needed for making sure the rival explanations are in fact correct.
the guy in overalls is on a two wheeled machine
woman sleeps under tree
All the dogs are laying down.
Maintenance workers are outside.
A man is working.
There is a man with a crocodile.