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').

Example Input: Stroke is the number ____ cause of death in the United States.\Question: Choose the right answer from options given a) ten b) nine c) one d) three
Example Output: d

Example Input: Breast cancer strikes one out of every ____ American women.\Question: Choose the right answer from options given a) one b) nine c) no d) six
Example Output: b

Example Input: Aspens are an important source of food and shelter for an estimated ____ hundred species.\Question: Choose the right answer from options given a) five b) seven c) four d) three
Example Output:
a