Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

Q: Fact: The gravitational pull of a natural satellite on Earth's oceans causes the tides. 
Question: The pull of what on the Earth's oceans cause the tides?

A: A natural satellite.
****
Q: Fact: Condoms make sex safe if they're not used incorrectly. 
Question: When aren't condoms safe?

A: When they're used incorrectly.
****
Q: Fact: A barometer is used to measure the force acting on a unit area. 
Question: What is used to measure the force acting on a unit area?

A:
a barometer.
****