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]: Calves can browse and follow their mother at three weeks old and are weaned at ____ months.\Question: Choose the right answer from options given a) five b) seven c) four d) three
[EX A]: a

[EX Q]: Most people believe that there are ____ kinds of taste - salt, sour, bitter, and sweet.\Question: Choose the right answer from options given a) four b) one c) zero d) five
[EX A]:
a