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: 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: Adaptation is considered to take place in one biological and ____ psychosocial modes.\Question: Choose the right answer from options given a) two b) three c) six d) nine
Example Output:
b