Question

Hello.
I wanted to ask what happens when a person dies.
From what I know, when there is no pulse and the line on the monitor is straight, they determine death.
But why, really, wouldn’t an atheist doctor keep trying to fix the material.
Of course there is damage to the material that is total loss, but it seems like the trigger is pulled too easily.
Maybe this is a silly question, but the shy person does not learn.