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:
Mechanical digestion occurs as ____ strong layers of muscle contract to produce a churning motion.\Question: Choose the right answer from options given a) four b) no c) three d) six

Ex Output:
c


Ex Input:
Nodes are points in space that have ____ probability for locating an electron there.\Question: Choose the right answer from options given a) no b) six c) zero d) three

Ex Output:
c


Ex Input:
Most fish can go a week to ____ days without food and be just fine.\Question: Choose the right answer from options given a) two b) ten c) five d) four

Ex Output:

b