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').

Example Input: 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
Example Output: b

Example Input: Twin souls are the last ____ souls to individualize.\Question: Choose the right answer from options given a) two b) ten c) zero d) six
Example Output: a

Example Input: Soybeans also supply all ____ essential amino acids needed by humans.\Question: Choose the right answer from options given a) ten b) two c) eight d) zero
Example Output:
c