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

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


[Q]: Morocco has _ perennial rivers and many dams have been built with potential for power generation.
[A]: four


[Q]: Asbestos is the name applied to _ naturally occurring minerals that are mined from the earth.
[A]:
six