It's used to form usually signs of possession of an object like "The girl's toy" or contractions like "it's" or "let's"
Answer:
I don't think I would be alive,there is no oxygen
It foreshadow that ceaser will be killed by his friends because they thought that he has absolute power and they will put there hands in his blood as a sin of victory
Saved as it's collective, he's collecting it
