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').

Many comets have ____ tails.\Question: Choose the right answer from options given a) two b) six c) three d) one
a

Cleavage is good in ____ directions forming cubes.\Question: Choose the right answer from options given a) two b) three c) six d) zero
b

Healthy lungs are an intricate weave of more than ____ hundred million tiny air sacs.\Question: Choose the right answer from options given a) two b) three c) no d) four

b