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

Output: d


Input: Consider Input: Diatoms look like ____ shells that fit together.\Question: Choose the right answer from options given a) zero b) one c) two d) seven

Output: c


Input: Consider Input: Seahorses are small fish with a life span of ____ to five years.\Question: Choose the right answer from options given a) three b) no c) ten d) one


Output: d