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

[EX Q]: Young groundhogs are weaned and ready to seek their own dens at _ to six weeks of age.
[EX A]: five

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

[EX Q]: Many astronauts have trouble adjusting to _ gravity.
[EX A]:
zero