All right, so what we're not talking about today, we are not talking about cancer, because i spent a lot of time talking about that and i'm really not interested. pausch tells his audience this because he wants them to know that

he has chosen not to focus on his cancer.

Explanation:

Randy Pausch, who was diagnosed with terminal pancreatic cancer, chooses to give one final lecture in order to leave both a personal and professional legacy.  In his last lecture, Pausch decides not to talk about cancer; instead, he summarizes the various life-lessons he learned throughout his life.

b)and

is the answer.

its because you eat a lot of food and that can lead to many heath problems like diabetes or becoming very over weight and fat etc.