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').

[EX Q]: Indian reservations are part of five of the nation's ____ poorest counties.\Question: Choose the right answer from options given a) seven b) nine c) ten d) two
[EX A]: c

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

[EX Q]: Smokers are ____ times more likely to have gum disease than nonsmokers are.\Question: Choose the right answer from options given a) six b) one c) four d) eight
[EX A]:
c