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

[Q]: Melanocytes are dendritic and are distributed roughly _ per six basal cells.
[A]: one


[Q]: Special relativity shows that time behaves surprisingly like the _ spatial dimensions.
[A]: three


[Q]: Biennials complete their life cycle in _ years a.
[A]:
two