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]: Female elephants have babies about ____ years apart, and they have only one each time.\Question: Choose the right answer from options given a) eight b) one c) zero d) three
[A]: d


[Q]: Nymphs emerge in ____ to seven days and flatten themselves against the leaf to feed.\Question: Choose the right answer from options given a) one b) five c) nine d) two
[A]: b


[Q]: Infertility is fairly common, and about one out of every ____ couples is infertile at any given time.\Question: Choose the right answer from options given a) two b) four c) nine d) six
[A]:
d