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]: 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]: Female cats come into heat cycles every ____ to four weeks during certain times of the year.\Question: Choose the right answer from options given a) eight b) ten c) zero d) three
[EX A]: d

[EX Q]: Many people have ____ symptoms until they suffer chest pains or a heart attack.\Question: Choose the right answer from options given a) three b) one c) no d) seven
[EX A]:
c