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

[EX Q]: Scientists use a characteristic to classify animals into _ groups.
[EX A]: two

[EX Q]: Prokaryotes mean they have _ nucleus in which they store genetic material.
[EX A]: no

[EX Q]: Hair transplantation is an office procedure that takes approximately three to _ hours.
[EX A]:
six