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]: Infants usually die of pneumonia or other infections before reaching ____ years of age.\Question: Choose the right answer from options given a) nine b) four c) zero d) eight
[A]: b


[Q]: China has about ____ in four of all smokers in the world.\Question: Choose the right answer from options given a) one b) seven c) ten d) six
[A]: a


[Q]: Sea lettuce goes through ____ reproductive phases.\Question: Choose the right answer from options given a) seven b) eight c) ten d) two
[A]:
d