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').

Ex 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

Ex Output:
b


Ex Input:
Most infected persons have ____ symptoms of disease.\Question: Choose the right answer from options given a) six b) no c) three d) one

Ex Output:
b


Ex Input:
Most lakes stratify into ____ layers during late spring, staying that way until late fall.\Question: Choose the right answer from options given a) seven b) one c) no d) three

Ex Output:

d