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]: Perennial grass takes three to ____ years before it is mature enough to produce adequate seed.\Question: Choose the right answer from options given a) five b) seven c) six d) four
[EX A]: a

[EX Q]: Most herbal formulas contain ____ to twelve herbs in various combinations.\Question: Choose the right answer from options given a) four b) no c) seven d) six
[EX A]: d

[EX Q]: Organic material means anything made up of ____ elements carbon, hydrogen, nitrogen, and oxygen.\Question: Choose the right answer from options given a) eight b) five c) four d) one
[EX A]:
c