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.
--------
Question: Fact: Heating with coal can cause air pollution. 
Question: Heating with coal can cause?

Answer: air pollution.


Question: Fact: sharks have tails. 
Question: What has a tail?

Answer: sharks.


Question: Fact: when iron rusts it becomes orange on the surface. 
Question: When iron rusts, it becomes what on the surface?

Answer:
orange.