Question

Alguém pode responder por favor?

Answer 1

Situation 1 : It happend probably , because she might've left the door opened. 
She could've locked every doors  and checked the house before she leaves*

Situation 2: he could've given more attention to her and perceive that his job it's not the only thing important in his life 

Situation 3: She probably forgot about the time , didn't pay attention. She could've setted an alarm clock to prevent that.

've = contraction for have