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

Q: Humans seem to be able to sense at least _ forms of energy.

A: eight
****
Q: Retinoic acid regulates oral epithelial differentiation by _ mechanisms.

A: two
****
Q: All ants have _ body parts, a pair of , elbowed antennae, six legs and a pinched waist.

A:
three
****