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: Some experts believe whining peaks around the ages of ____ or four.\Question: Choose the right answer from options given a) three b) no c) four d) seven
Example Output: a

Example Input: Colon cancer has ____ main symptom complexes.\Question: Choose the right answer from options given a) four b) five c) two d) ten
Example Output:
a