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:
Islamic practice is based on what are called the ____ pillars of faith.\Question: Choose the right answer from options given a) eight b) one c) five d) four

Ex Output:
c

Ex Input:
Reliability affects the production of goods in ____ distinct ways.\Question: Choose the right answer from options given a) one b) eight c) six d) three

Ex Output:
d

Ex Input:
All vertebrates produce interferons, and all appear to produce the ____ major classes.\Question: Choose the right answer from options given a) seven b) ten c) five d) three

Ex Output:
d