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]: Hamsters can live to be three to ____ years old.\Question: Choose the right answer from options given a) four b) two c) three d) nine
[EX A]: a

[EX Q]: Insects have ____ common types of metamorphosis.\Question: Choose the right answer from options given a) six b) eight c) two d) seven
[EX A]: c

[EX Q]: Federal law requires all children under ____ years old to wear a lifejacket.\Question: Choose the right answer from options given a) no b) six c) seven d) nine
[EX A]:
c