Part A: What event sets the main action of the story in motion? Arthur’s argument with norma over the button unit

A . Arthur’s argument with Norma over the button unit .

Explanation:

In the short story Button Button by Richard Matheson, the Lewises have their fair share of confusing opinions after they were 'gifted' a package by an international organization that 'rewards' anyone who presses the button inside the package. The arrival of the package at the Lewises' residence bring forth the start of the cycle of the story.

After Mr. Steward delivered the key to the button, Norma was intrigued by the very notion of being rewarded $50,000. While her husband Arthur did not even want to think or talk further about it, Norma kept on pestering him with the topic, frequently asking "Aren't you curious at all?", "Doesn't it intrigue you?", "Wouldn't you like to know?". And with her interest in checking out the authenticity of the offer, she and Arthur began an argument with Arthur vehemently denying any interest in it. This argument over the button unit sets the main action of the story in motion.

Thus, the correct answer is option A.