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: Classes play ____ distinct roles in object-oriented programming.\Question: Choose the right answer from options given a) eight b) zero c) two d) no

A: c
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Q: Heme is made of ____ pyrrole groups united to form a porphyrin ring.\Question: Choose the right answer from options given a) five b) four c) eight d) six

A: b
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Q: Man therefore has ____ different substances interacting with each other.\Question: Choose the right answer from options given a) one b) seven c) two d) ten

A:
c
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