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:
Government buildings fly flags of the ____ nations.\Question: Choose the right answer from options given a) ten b) no c) seven d) two

Ex Output:
d

Ex Input:
Young children suffer from an average of six to ____ colds a year.\Question: Choose the right answer from options given a) ten b) eight c) two d) one

Ex Output:
b

Ex Input:
Sleep apnea is ____ times more prevalent in men than in women.\Question: Choose the right answer from options given a) seven b) three c) one d) six

Ex Output:
b