instruction:
In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
question:
Retinoic acid regulates oral epithelial differentiation by _ mechanisms.
answer:
two


question:
Hoatzin has typical foot with _ toes forwards and one backwards.
answer:
three


question:
Giraffes have two horns and _ or three knobs.
answer:

two