Complete the restaurant manager's tragic recounting of a disastrous dinner service.

By the time the notoriously harsh food critic arrived at our humble diner, Chef Marcel _____ three dozen eggs onto the kitchen floor and was on the verge of a complete nervous breakdown.

The correct answer is had dropped.

We use the Past Perfect Simple (had + past participle) to describe a completed action that happened before another event in the past (the critic's arrival).

Even though this sounds like a chaotic, ongoing situation, we cannot use the continuous form (had been dropping) when we specify the exact quantity of completed actions or items ("three dozen eggs"). Dropped alone is incorrect because the "By the time..." clause requires the past perfect to establish the sequence of events.