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').

Input: Consider Input: All mass spectrometers consist of ____ distinct regions.\Question: Choose the right answer from options given a) three b) one c) two d) zero

Output: a


Input: Consider 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

Output: c


Input: Consider Input: Tree swallows arrive in spring before any of the ____ other species of swallows.\Question: Choose the right answer from options given a) eight b) five c) zero d) no


Output: b