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: Aridity presents ____ main obstacles to solitary behavior.\Question: Choose the right answer from options given a) no b) three c) two d) five

Output: c


Input: Consider Input: Marriage is the legal union of ____ people.\Question: Choose the right answer from options given a) one b) no c) five d) two

Output: d


Input: Consider Input: Astrophysicists know that ____ times as much dark matter exists in the universe.\Question: Choose the right answer from options given a) eight b) no c) one d) ten


Output: a