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').

Input: Consider Input: Altimetric satellites are usually limited life missions lasting approximately three to ____ years.\Question: Choose the right answer from options given a) five b) ten c) four d) eight

Output: b


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

Output: b


Input: Consider Input: Cats have five toes on their forefeet and ____ toes on their hind feet.\Question: Choose the right answer from options given a) no b) three c) four d) five


Output: c