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: Calves can browse and follow their mother at three weeks old and are weaned at ____ months.\Question: Choose the right answer from options given a) five b) seven c) four d) three
Example Output: a

Example Input: Carnations grow well in a garden spot that receive ____ to five hours of sunlight per day.\Question: Choose the right answer from options given a) eight b) three c) one d) four
Example Output: d

Example Input: Ants are social insects, and most colonies contain ____ castes - queens, males, and workers.\Question: Choose the right answer from options given a) five b) three c) two d) ten
Example Output:
b