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:
Ground squirrels breed once a year, averaging ____ to eight per litter.\Question: Choose the right answer from options given a) seven b) one c) six d) ten

Ex Output:
a


Ex Input:
Copper is ____ times higher in dog liver than in human liver.\Question: Choose the right answer from options given a) three b) ten c) six d) one

Ex Output:
b


Ex Input:
Pakistani expatriates play an important role in the economies of the ____ Arab Gulf countries.\Question: Choose the right answer from options given a) two b) eight c) four d) six

Ex Output:

d