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]: Many scientists believe the neutrino has ____ mass at all.\Question: Choose the right answer from options given a) eight b) zero c) two d) no
[A]: d


[Q]: Astronauts sleep only ____ hours each night, on average.\Question: Choose the right answer from options given a) six b) one c) four d) seven
[A]: a


[Q]: Movement is aided by ____ sets of longitudinal muscles that extend throughout the entire body.\Question: Choose the right answer from options given a) nine b) two c) four d) zero
[A]:
c