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: Elephants have four molars, which are replaced ____ times, for a total of six sets in a lifetime.\Question: Choose the right answer from options given a) five b) no c) three d) one
Example Output: a

Example Input: Water is present in all ____ phases in Earth s atmosphere.\Question: Choose the right answer from options given a) six b) nine c) two d) three
Example Output: d

Example Input: Some plants have three or ____ tunnels per stalk.\Question: Choose the right answer from options given a) three b) eight c) four d) one
Example Output:
c