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: Many tractors have ____ wheel drive to get extra grip on the hills and in wet conditions.\Question: Choose the right answer from options given a) four b) seven c) five d) two

Output: a


Input: Consider Input: Heme is made of ____ pyrrole groups united to form a porphyrin ring.\Question: Choose the right answer from options given a) five b) four c) eight d) six

Output: b


Input: Consider Input: Some wolves can live up to ____ years.\Question: Choose the right answer from options given a) eight b) zero c) ten d) no


Output: c