Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[EX Q]: Slimy smear does the bacteria look when seen with the naked eye.
[EX A]: How does the bacteria look when seen with the naked eye?

[EX Q]: A student should use a balance to compare the masses of two small rocks.
[EX A]: Which tool should a student use to compare the masses of two small rocks?

[EX Q]: Substances that cannot be broken down into simpler substances with different properties are called elements.
[EX A]:
What are substances that cannot be broken down into simpler substances with different properties called?