Turn the given fact into a question by a simple rearrangement of words. This typically involves replacing some part of the given fact with a WH word. For example, replacing the subject of the provided fact with the word "what" can form a valid question. Don't be creative! You just need to rearrange the words to turn the fact into a question - easy! Don't just randomly remove a word from the given fact to form a question. Remember that your question must evaluate scientific understanding. Pick a word or a phrase in the given fact to be the correct answer, then make the rest of the question. You can also form a question without any WH words. For example, "A radio converts electricity into?"

Input: Consider Input: Fact: amphioxus larvae are free-swimming.

Output: What type of larvae are free-swimming?


Input: Consider Input: Fact: Vertebrates have a complete digestive system and a closed circulatory system.

Output: What do all vertebrates have?


Input: Consider Input: Fact: smallpox is so small that it can be seen only with an electron microscope.


Output: What is so small it can be seen only with an electron microscope?