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]: Antibodies contain ____ pairs of protein chains.\Question: Choose the right answer from options given a) no b) two c) nine d) zero
[EX A]: b

[EX Q]: Asthma accounts for ____ in six of all pediatric emergency visits in the United States.\Question: Choose the right answer from options given a) four b) seven c) one d) six
[EX A]: c

[EX Q]: Batteries contain hydrogen and oxygen, ____ flammable and explosive gasses.\Question: Choose the right answer from options given a) four b) five c) seven d) two
[EX A]:
d