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: Scorpions also have ____ legs.\Question: Choose the right answer from options given a) eight b) zero c) nine d) ten
Example Output: a

Example Input: Younger children can produce as much as ____ times more saliva than adults.\Question: Choose the right answer from options given a) one b) ten c) five d) eight
Example Output: d

Example Input: Protons are heavy particles made of ____ quarks .\Question: Choose the right answer from options given a) zero b) three c) eight d) one
Example Output:
b