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: Pups remain in the den for about ____ weeks, and are cared for by the entire pack.\Question: Choose the right answer from options given a) ten b) three c) six d) no
Example Output: c

Example Input: Chemical interactions are essentially electron interactions of ____ atoms.\Question: Choose the right answer from options given a) six b) no c) ten d) two
Example Output: d

Example Input: Children grow outward emotionally between ____ and five years of age.\Question: Choose the right answer from options given a) six b) four c) no d) eight
Example Output:
b