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

[EX Q]: Pelagic division is divided into neritic and _ levels of pelagic provinces.
[EX A]: three

[EX Q]: Tin exists in _ allotropic forms.
[EX A]: three

[EX Q]: Gene flow plays a crucial role in all _ stages.
[EX A]:
three