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]: Quarks also come in ____ 'colours', terms for a property a little like electrical charge.\Question: Choose the right answer from options given a) three b) nine c) six d) no
[A]: a


[Q]: Real airplanes have round engines and ____ wings.\Question: Choose the right answer from options given a) four b) six c) three d) two
[A]: d


[Q]: Reclaimed water is sewage water that has been treated and disinfected using ____ different methods.\Question: Choose the right answer from options given a) three b) zero c) four d) eight
[A]:
c