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').

[Q]: Astronomers fall in ____ classes - professionals and amateurs.\Question: Choose the right answer from options given a) two b) four c) six d) zero
[A]: a


[Q]: Perennial grass takes ____ to five years before it is mature enough to produce adequate seed.\Question: Choose the right answer from options given a) six b) zero c) three d) no
[A]: c


[Q]: Liposomes have ____ main advantages over plain dry capsule or tablet delivery methods.\Question: Choose the right answer from options given a) no b) three c) four d) seven
[A]:
b