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

Example Input: Retinoic acid regulates oral epithelial differentiation by _ mechanisms.
Example Output: two

Example Input: Roundworms are fairly large worms that can grow to be _ or five inches long.
Example Output: four

Example Input: Milk proteins can cause colic, a digestive upset that bothers one in _ infants.
Example Output:
five