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: Stable oxygen has eight protons and ____ neutrons.\Question: Choose the right answer from options given a) eight b) ten c) three d) zero
Example Output: a

Example Input: Ants have ____ distinct body parts.\Question: Choose the right answer from options given a) nine b) zero c) no d) three
Example Output: d

Example Input: Nurseries provide care for children under ____ years old.\Question: Choose the right answer from options given a) three b) ten c) seven d) five
Example Output:
d