instruction:
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?"
question:
Fact: narcotic analgesics act on most invertebrates to relieve pain.
answer:
How do most analgesics work on invertebrates?


question:
Fact: looseness of soil helps plants survive.
answer:
What helps plants survive?


question:
Fact: Optical tools are used for observing things that are smaller than they appear.
answer:

Optical tools are used for observing things that are smaller than what?