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]: Reverse osmosis uses three to ____ gallons of water to produce one gallon of drinking water.\Question: Choose the right answer from options given a) six b) eight c) five d) ten
[EX A]: d

[EX Q]: Big bluestem grows up to ____ feet tall.\Question: Choose the right answer from options given a) seven b) no c) nine d) eight
[EX A]: c

[EX Q]: Binary distillation is a separation of only ____ chemicals.\Question: Choose the right answer from options given a) ten b) two c) four d) zero
[EX A]:
b