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').

Kabbalists group the simple letters into ____ triplets.\Question: Choose the right answer from options given a) four b) no c) ten d) three
a

Selenium is ____ times more poisonous than arsenic.\Question: Choose the right answer from options given a) one b) five c) eight d) two
b

Some manatees have ____ or four nails on the tip of each flipper.\Question: Choose the right answer from options given a) eight b) zero c) six d) three

d