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

[EX Q]: Many people have ____ symptoms until they suffer chest pains or a heart attack.\Question: Choose the right answer from options given a) three b) one c) no d) seven
[EX A]: c

[EX Q]: Plants grow approximately six to ____ feet tall.\Question: Choose the right answer from options given a) four b) ten c) seven d) eight
[EX A]:
b