Complete the roommates' argument about the kitchen disaster by choosing the correct phrase for each blank.

"Okay, I'm not mad, I just want to understand. What exactly happened to our poor microwave?"

"And what on earth did you put inside it that caused this massive explosion?"

"What exactly happened to our poor microwave?"

This is a subject question. "What" acts as the subject (the thing that happened). In past simple subject questions, we use the past tense verb directly ("happened") without the auxiliary "did."

"And what on earth did you put inside it that caused this massive explosion?"

This is an object question. "You" is the subject performing the action, and "what" is the object being placed in the microwave. Therefore, we use the auxiliary verb "did" (Question Word + did + Subject + Base Verb).