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?"

[Q]: Fact: protective plates over the ends of the fingers are made of keratin.
[A]: Protective plates over the ends of the fingers are made of what?


[Q]: Fact: Earthworm burrows help aerate soil, which is essential for growing plants.
[A]: Earthworm burrows help aerate soil, which is essential for what?


[Q]: Fact: Hydrogen bonds cause ice to expand as it is formed.
[A]:
What causes ice to expand as it is formed?