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]: Tetrapods are animals that have ____ legs or leg-like appendages.\Question: Choose the right answer from options given a) four b) one c) ten d) six
[A]: a


[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
[A]: b


[Q]: Earwigs have ____ molts in the year before they become adults.\Question: Choose the right answer from options given a) ten b) one c) three d) five
[A]:
d