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

[Q]: Cats There are thirty _ recognised species of cats and a whole host of subspecies or races.
[A]: five

[Q]: Ozone is a form of oxygen in which the molecule contains _ atoms instead of two.
[A]: three

[Q]: Otters are long and slim animals with _ short legs that can be longer than a meter .
[A]:
four