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]: Background radiation comes from ____ sources.\Question: Choose the right answer from options given a) zero b) three c) four d) no
[A]: b


[Q]: Millipedes have ____ pairs of legs on each body segment.\Question: Choose the right answer from options given a) seven b) ten c) six d) two
[A]: d


[Q]: Colds tend to last seven to ____ days, while allergies can go on for weeks.\Question: Choose the right answer from options given a) ten b) zero c) four d) six
[A]:
a