In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
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Question: New species are believed to arrive in the Mediterranean at the rate of _ to five annually.

Answer: four


Question: Some dentists prefer using the oral rinse for _ to five days at a time.

Answer: three


Question: Infiltration requires immersing tissues in _ changes of melted paraffin.

Answer:
two