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: Chlorine is manufactured in ____ ways.\Question: Choose the right answer from options given a) four b) two c) nine d) seven
Example Output: b

Example Input: Surface area is the sum of the faces, or surfaces, of a ____ dimensional shape.\Question: Choose the right answer from options given a) no b) eight c) three d) six
Example Output:
c