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

Q: Essential oils have a non-toxic, residual effect of up to five months from just _ application.

A: one
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Q: Humans host _ species of louse, the head louse , the body louse and the pubic louse .

A: three
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Q: Marakoopa cave is a large cavern with _ underground streams.

A:
two
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