Asking how Shelley "presents" choices is vague, and could be treated in many ways, so I'm not sure I'll hit what you or your teacher are after. I can detail two aspects of the choices that Frankenstein makes in the novel named after him, though.
First, Victor often thinks he is making the high-minded, correct decision. When he chooses to make the creature, he thinks he is furthering science and contributing to great discoveries. He is doing what no on else can do. When he chooses to destroy the female creature he thinks he is standing up to and against evil--the creature. He thinks he is saving the world by not trusting the creature to keep his word and not wreak havoc on humans with his new partner. He thinks he knows more than others and he knows what is moral. But his decisions turn out to be immoral and unjust.
Second, but related, is the irresponsibility of his decisions. The two decisions mentioned above are irresponsible, of course, as is the decision to not recognize and nurture the creature he fathers. Without nurture, the creature turns into a monster. Victor owns much of the responsibility for this. His decision to leave his wife alone on their wedding night is also irresponsible. He would have fought the creature and risked his life for her, but his self-centeredness prohibits him from considering her as at risk. He sees only himself as the focus of the creature's plans.
Again, I don't know if what I've written is the kind of thing you were after, but I hope I came close.