TASK DEFINITION: In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
PROBLEM: Some manatees have _ or four nails on the tip of each flipper.

SOLUTION: three

PROBLEM: Corals are _ fold.

SOLUTION: two

PROBLEM: Retinoic acid regulates oral epithelial differentiation by _ mechanisms.

SOLUTION:
two