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').

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

Ex Output:
d


Ex Input:
Respiratory therapists complete two to ____ years of education.\Question: Choose the right answer from options given a) no b) one c) four d) eight

Ex Output:
c


Ex Input:
Most leaflets have ____ to three coarse teeth near their base.\Question: Choose the right answer from options given a) one b) no c) nine d) five

Ex Output:

a