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').
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Question: Natural tellurium consists of ____ isotopes.\Question: Choose the right answer from options given a) six b) seven c) eight d) one

Answer: c


Question: Most herbal formulas contain ____ to twelve herbs in various combinations.\Question: Choose the right answer from options given a) four b) no c) seven d) six

Answer: d


Question: Many dogs show no problems until they are six to ____ years old or older.\Question: Choose the right answer from options given a) eight b) nine c) six d) three

Answer:
a