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]: Ozone is a molecule containing ____ oxygen atoms.\Question: Choose the right answer from options given a) one b) nine c) no d) three
[EX A]: d

[EX Q]: Government buildings fly flags of the ____ nations.\Question: Choose the right answer from options given a) ten b) no c) seven d) two
[EX A]: d

[EX Q]: Most birds have ____ toes, three that face forward and one rearward.\Question: Choose the right answer from options given a) two b) ten c) nine d) four
[EX A]:
d