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]: 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

[EX Q]: Songbirds have ____ sets of vocal chords.\Question: Choose the right answer from options given a) six b) two c) eight d) ten
[EX A]: b

[EX Q]: Internet phone uses ____ computers and an internet connection.\Question: Choose the right answer from options given a) zero b) nine c) five d) two
[EX A]:
d