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.

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

Fact: cattle can have a negative impact on the environment. 
Question: what can have a negative impact on the environment?
cattle.

Fact: Microscopes are used for observing materials up close. 
Question: what are used for observing materials up close?

microscopes.