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]: Vision disorders affect ____ in every four school-age children.\Question: Choose the right answer from options given a) nine b) one c) five d) six
[A]: b


[Q]: Calves can swim ____ days after they are born.\Question: Choose the right answer from options given a) ten b) two c) zero d) one
[A]: b


[Q]: Aquifers occur in ____ types of geologic formations.\Question: Choose the right answer from options given a) zero b) seven c) two d) five
[A]:
c