Final answer:
In 'Because of Mr. Terupt', it was Luke who threw the snowball that changed everything.
Step-by-step explanation:
In the book 'Because of Mr. Terupt', the snowball that changed everything was thrown by Luke.
Luke, one of the main characters in the book, impulsively throws a snowball at Mr. Terupt, their new teacher, during a recess. This snowball incident sets off a chain of events that leads to significant changes in the lives of the characters and the dynamics of the class.
Luke's action and its consequences are central to the plot of the story and it serves as a turning point in the narrative.