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]: Government buildings fly flags of the ____ nations.\Question: Choose the right answer from options given a) ten b) no c) seven d) two
[EX A]: d

[EX Q]: Routers are basically systems, which connect ____ networks together.\Question: Choose the right answer from options given a) three b) two c) nine d) six
[EX A]: b

[EX Q]: Troxel helmets have ____ padding systems.\Question: Choose the right answer from options given a) one b) zero c) eight d) two
[EX A]:
d