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').
--------
Question: Chlorine has ____ naturally occurring isotopes.\Question: Choose the right answer from options given a) nine b) eight c) three d) two

Answer: d


Question: Owls have ____ toes on each foot, like most birds.\Question: Choose the right answer from options given a) no b) seven c) four d) one

Answer: c


Question: Oral tolerance is induced by at least ____ mechanisms.\Question: Choose the right answer from options given a) three b) two c) eight d) five

Answer:
b