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: Serial transfer is the sequential transmission of the ____ bit-voltages that constitute a byte.\Question: Choose the right answer from options given a) ten b) eight c) two d) four
Example Output: b

Example Input: Ossification begins up to ____ months before birth.\Question: Choose the right answer from options given a) nine b) seven c) three d) six
Example Output: b

Example Input: Guppies are usually able to first breed by the age of ____ months.\Question: Choose the right answer from options given a) no b) three c) six d) two
Example Output:
b