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').

[EX Q]: Females inherit ____ X chromosomes, one from each parent.\Question: Choose the right answer from options given a) five b) two c) no d) seven
[EX A]: b

[EX Q]: Atoms are extremely small, on the order of a few ____ billionths of a meter.\Question: Choose the right answer from options given a) ten b) seven c) nine d) eight
[EX A]: a

[EX Q]: Youth unemployment is ____ times the adult level.\Question: Choose the right answer from options given a) one b) three c) seven d) no
[EX A]:
b