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: Collars come in ____ shapes.\Question: Choose the right answer from options given a) six b) two c) four d) zero
Example Output: b

Example Input: Illiteracy is ____ percent higher among women than men.\Question: Choose the right answer from options given a) seven b) six c) zero d) five
Example Output: a

Example Input: Engine oil has ____ main functions.\Question: Choose the right answer from options given a) zero b) three c) ten d) eight
Example Output:
b