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

Q: New species are believed to arrive in the Mediterranean at the rate of _ to five annually.

A: four
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Q: Mice are fertile animals because female mice come into heat every _ to five days.

A: four
****
Q: Odors elicit _ different oscillations in the turtle olfactory bulb .

A:
three
****