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

Q: Rheas are brownish instead of black like the ostrich and have _ toes instead of two.

A: three
****
Q: Professional chefs use _ tools to keep knives sharp.

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

A:
four
****