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').

[Q]: Mechanical stability comes from having fused quartz, in ____ gravity, cold.\Question: Choose the right answer from options given a) five b) zero c) six d) two
[A]: b


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


[Q]: Crustaceans have ____ types of feelers.\Question: Choose the right answer from options given a) two b) one c) eight d) zero
[A]:
a