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

Input: Consider Input: Animals develop either two or _ embryonic germs layers .

Output: three

Input: Consider Input: Thermal equilibrium occurs when _ bodies have the same temperature.

Output: two

Input: Consider Input: Most dens are oval shape, six to nine feet long and about _ feet in height and width.
Output: six