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]: Female bilbies have a backward-opening pouch with ____ nipples.\Question: Choose the right answer from options given a) no b) two c) five d) eight
[A]: d


[Q]: Organisms have ____ forms of nucleic acid.\Question: Choose the right answer from options given a) four b) three c) two d) one
[A]: c


[Q]: Nitrites are the more dangerous of the ____ compounds.\Question: Choose the right answer from options given a) one b) two c) three d) seven
[A]:
b