Given a sentence with a missing word, pick the answer option that best fills out the missing word in the sentence. Indicate each answer with its index ('a', 'b', 'c', 'd').

Q: Heat pumps give off ____ fumes or harmful products of combustion.\Question: Choose the right answer from options given a) four b) zero c) six d) no

A: d
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Q: Female cats come into heat cycles every ____ to four weeks during certain times of the year.\Question: Choose the right answer from options given a) eight b) ten c) zero d) three

A: d
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Q: Potential energy is divided into ____ different types of energy.\Question: Choose the right answer from options given a) eight b) three c) zero d) two

A:
b
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