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]: Diatoms look like ____ shells that fit together.\Question: Choose the right answer from options given a) zero b) one c) two d) seven
[A]: c


[Q]: Statistics show that within ____ years of divorce, many people marry a second time.\Question: Choose the right answer from options given a) four b) nine c) six d) three
[A]: d


[Q]: Fruit trees are usually safe after ____ years.\Question: Choose the right answer from options given a) five b) four c) no d) three
[A]:
d