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 endocrinologists see patients every ____ months throughout the pregnancy.\Question: Choose the right answer from options given a) six b) two c) zero d) three
[EX A]: b

[EX Q]: Poles CAN occur at ____ frequency.\Question: Choose the right answer from options given a) six b) four c) zero d) eight
[EX A]: c

[EX Q]: Older trees are more difficult to train, as bending mature branches can take ____ to three years.\Question: Choose the right answer from options given a) zero b) one c) nine d) seven
[EX A]:
b