They have developed the theory (claim)​

the answers are:

1. dolores driscoll - b. first person minor

dolores is a minor character who happens to be driving the bus at the time of the accident. she narrates picking up each of the children and her last memory is the children being thrown around the bus.

2. billy ansel - a. first person major

billy loses his twins in the accident. he tells his own story, how he witnessed the accident and how he tried to the rescuers. he is a major character, as he is at the center of the story.

3. mitchell stephens - c. first person observer

mitchell enters the story after the accident. he is a lawyer who learns about the accident based on other characters observations. though he tells the story from a first person perspective, he is just an observer.

as for matcthing the message or lesson posted with the person who said them:

1."obviously, you can't control everything, but you are obliged to take care of the few things you can. i'm an optimist basically who acts like a pessimist. on principle. just in case." - dolores driscoll

2. "i could no longer believe even in life. . for me now the only reality was death." - billy ansel

3 is blunder, i’m not sure about the last one but the first two look correct