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:
Natural indium contains ____ isotopes.\Question: Choose the right answer from options given a) one b) eight c) two d) seven

Ex Output:
c


Ex Input:
Stringers consist of ____ narrow pieces of wood glued together.\Question: Choose the right answer from options given a) ten b) three c) five d) seven

Ex Output:
b


Ex Input:
Piano duets are for ____ players at one piano .\Question: Choose the right answer from options given a) two b) six c) nine d) four

Ex Output:

a