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]: Most children experience at least one episode by the time they are ____ years old.\Question: Choose the right answer from options given a) eight b) one c) ten d) seven
[EX A]: d

[EX Q]: Mosquitoes have ____ distinctive life stages, with the first three stages being spent in the water.\Question: Choose the right answer from options given a) four b) zero c) nine d) five
[EX A]: a

[EX Q]: All birds have two legs with ____ toes each.\Question: Choose the right answer from options given a) four b) six c) one d) zero
[EX A]:
a