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

[Q]: Metals often crystallize in a _ dimensional version of the hexagonal closest packed structure.
[A]: three


[Q]: Essential oils have a non-toxic, residual effect of up to five months from just _ application.
[A]: one


[Q]: Fats pack _ calories per gram compared to four for carbohydrates.
[A]:
nine