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

Example Input: Gestation is _ to nine months long, after which a single calf is born.
Example Output: eight

Example Input: Induction also operates early in development, even before the _ layered embryo forms.
Example Output: three

Example Input: Birds of prey have _ toes on each foot.
Example Output:
four