B) When the waiter slipped on the puddle of water.
Explanation:
This is a fragment because it is a dependent clause. Sentences must contain at least one independent clause, which contains a subject and verb and is a complete thought. Because this fragment starts with the word "when," it cannot be a full sentence, because the thought is not complete. For it to be a sentence, it would have to say something like "When the waiter slipped on the puddle of water<em>, he dropped his tray full of food</em>." Hope this helps!
