In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

[Q]: Walruses walk with _ flippers over ice and snow.
[A]: four


[Q]: Birds begin dying of fowl cholera _ to nine days after exposed to the virus.
[A]: four


[Q]: Acupressure is similar to acupuncture except _ needles are used.
[A]:
no