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: Insects have ____ common types of metamorphosis.\Question: Choose the right answer from options given a) six b) eight c) two d) seven
Example Output: c

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: Utilitarianism has ____ moral concepts, equality and utility.\Question: Choose the right answer from options given a) two b) ten c) one d) five
Example Output:
a