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: Perennial grass takes three to ____ years before it is mature enough to produce adequate seed.\Question: Choose the right answer from options given a) five b) seven c) six d) four
Example Output: a

Example Input: Most school aged children pass at least ____ stools per week, with an average of one stool per day.\Question: Choose the right answer from options given a) three b) one c) six d) zero
Example Output: a

Example Input: Most sailing ships have between ____ and three mast but some have four.\Question: Choose the right answer from options given a) seven b) eight c) one d) ten
Example Output:
c