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]: Cats have ____ sets of vocal cords.\Question: Choose the right answer from options given a) zero b) nine c) two d) three
[A]: c


[Q]: Elk retain their antlers for more than ____ months of the year.\Question: Choose the right answer from options given a) nine b) ten c) six d) seven
[A]: c


[Q]: Industrial halocarbons are effective ozone-depleters for ____ reasons.\Question: Choose the right answer from options given a) three b) two c) eight d) ten
[A]:
b