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:
Habitat destruction is a concern for all ____ gorilla subspecies.\Question: Choose the right answer from options given a) no b) four c) three d) five

Ex Output:
b


Ex Input:
Kabbalists group the simple letters into ____ triplets.\Question: Choose the right answer from options given a) four b) no c) ten d) three

Ex Output:
a


Ex Input:
Normal adults appear to require ____ to eight hours of sleep per day on average.\Question: Choose the right answer from options given a) ten b) six c) zero d) three

Ex Output:

b