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: Songbirds have ____ sets of vocal chords.\Question: Choose the right answer from options given a) six b) two c) eight d) ten
Example Output: b

Example Input: Laparoscopic surgery is performed via three or ____ small incisions in the abdomen.\Question: Choose the right answer from options given a) nine b) six c) five d) four
Example Output: d

Example Input: Calves are weaned when they are about ____ to eight months old.\Question: Choose the right answer from options given a) four b) two c) one d) seven
Example Output:
d