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: Vaccination typically occurs at ____ to eight weeks of age in kittens.\Question: Choose the right answer from options given a) three b) nine c) six d) no
Example Output: c

Example Input: Dogs are pack animals, and ____ dogs is the minimum number for proper socialization.\Question: Choose the right answer from options given a) four b) five c) no d) zero
Example Output: b

Example Input: Caterpillars feed actively on broadleaf trees for ____ to six weeks.\Question: Choose the right answer from options given a) ten b) eight c) two d) five
Example Output:
d