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 tellurium consists of ____ isotopes.\Question: Choose the right answer from options given a) six b) seven c) eight d) one

Ex Output:
c


Ex Input:
Most females are sexually mature at about ____ to six years.\Question: Choose the right answer from options given a) eight b) nine c) five d) two

Ex Output:
c


Ex Input:
Recycling plastic uses only five to ____ percent as much energy as manufacturing new plastic.\Question: Choose the right answer from options given a) two b) ten c) no d) zero

Ex Output:

b