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]: Carbon can bond to a maximum of ____ atoms.\Question: Choose the right answer from options given a) six b) ten c) five d) four
[EX A]: d

[EX 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
[EX A]: c

[EX Q]: Ethanol typically adds ____ octane numbers when blended with gasoline.\Question: Choose the right answer from options given a) seven b) no c) five d) three
[EX A]:
d