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: Real airplanes have round engines and ____ wings.\Question: Choose the right answer from options given a) four b) six c) three d) two
Example Output: d

Example Input: TriMetal Irons Discover the benefits of ____ different metals.\Question: Choose the right answer from options given a) five b) seven c) no d) three
Example Output: d

Example Input: Female lemmings give birth to the baby lemmings after a gestation period of around ____ weeks.\Question: Choose the right answer from options given a) no b) six c) three d) four
Example Output:
c