Rezones porque la ambición puede ser peligrosa?

Use who. if it wasn't a question, you could put the he in the blank.  if you can put he or she in the blank, it's who.if you can put him or her in the blank, it's whom.

Prewriting: this stage of the writing process involve gathering and selecting ideas; teachers can students in several ways: creating lists, researching, brainstorming,reading to discover more about the author's style, talking, collecting memorabilia or clips from other texts, and free-writingdrafting: in this stage, students begin writing, connecting, and developing ideasrevising: this is the stage of writing that involves rewriting or "re-seeing; " emphasis is place on examining sentence structure, word choice, voice, and organization of the pieceediting: this stage involves checking for style and conventions--spelling, grammar, usage, and punctuationpublishing: the "going public" stage of writingevaluating: in this stage, the writer looks back at his/her work and self-evaluates, and the audience evaluates the effectiveness of the writingwriting activities : personal writing, workplace writing, subject writing, creative writing, persuasive writing, and scholarly writingpeer review: acting a referee; evaluating a colleague's work professionally