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: Western culture offers only ____ genders, man or woman.\Question: Choose the right answer from options given a) three b) two c) one d) four
Example Output: b

Example Input: Elephants give birth to one calf every ____ to nine years on average.\Question: Choose the right answer from options given a) no b) four c) three d) seven
Example Output: b

Example Input: Graphics fall into ____ categories, raster and vector.\Question: Choose the right answer from options given a) nine b) six c) two d) eight
Example Output:
c