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: Healthcare providers diagnose ____ general types of insomnia.\Question: Choose the right answer from options given a) two b) eight c) one d) three
Example Output: a

Example Input: Centrifugal pumps can usually handle up to about ____ percent by volume of air.\Question: Choose the right answer from options given a) one b) five c) eight d) seven
Example Output: b

Example Input: Infections are uncommon before ____ weeks of age - breast feeding seems to be somewhat protective.\Question: Choose the right answer from options given a) six b) eight c) two d) five
Example Output:
a