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

[EX Q]: Water is the only substance on earth that exists naturally in _ states .
[EX A]: three

[EX Q]: Flexible shapes are also shapes which have _ obvious way of being attacked.
[EX A]: no

[EX Q]: Some kinds complete the life cycle in less than a year, while others require up to _ years.
[EX A]:
four