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: Batteries consist of ____ electrodes immersed in an electrolyte.\Question: Choose the right answer from options given a) two b) eight c) three d) seven
Example Output: a

Example Input: Cougars have ____ toes with three distinct lobes present at the base of the pad.\Question: Choose the right answer from options given a) no b) four c) eight d) zero
Example Output: b

Example Input: Heavy rain falls at a rate greater than ____ millimetres per hour.\Question: Choose the right answer from options given a) zero b) four c) three d) two
Example Output:
b