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: Minks travel more than most furbearers, covering up to ____ miles a night.\Question: Choose the right answer from options given a) four b) five c) zero d) ten
Example Output: d

Example Input: Water covers ____ thirds of the planet's surface.\Question: Choose the right answer from options given a) eight b) three c) two d) six
Example Output:
c