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').

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
b

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
d

Natural tantalum contains ____ isotopes.\Question: Choose the right answer from options given a) two b) zero c) eight d) three

a