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

Ex Output:
a


Ex Input:
Japan is a highly urbanised country, with approximately three in every ____ people living in cities.\Question: Choose the right answer from options given a) seven b) two c) four d) eight

Ex Output:
c


Ex Input:
Earthworms are about ____ to five inches in length.\Question: Choose the right answer from options given a) no b) four c) six d) seven

Ex Output:

b