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]: Most internal parasites are specific to one or ____ species.\Question: Choose the right answer from options given a) seven b) three c) two d) five
[EX A]: c

[EX Q]: Most smokers try to quit at least ____ or six times before they succeed, researchers say.\Question: Choose the right answer from options given a) nine b) three c) seven d) five
[EX A]:
d