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]: Chacoan peccaries are the largest of the ____ peccary species.\Question: Choose the right answer from options given a) eight b) three c) ten d) no
[EX A]: b

[EX Q]: Carbon has ____ isotopes.\Question: Choose the right answer from options given a) nine b) two c) four d) no
[EX A]:
b