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').

[EX 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
[EX A]: a

[EX Q]: ATMs are expensive machines with an average useful life of ____ to fifteen years.\Question: Choose the right answer from options given a) nine b) eight c) ten d) two
[EX A]: c

[EX Q]: Infertility affects about ____ in six couples of child-bearing age.\Question: Choose the right answer from options given a) three b) one c) eight d) seven
[EX A]:
b