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

[EX Q]: Humans brains are about _ times bigger than in chimpanzees.
[EX A]: three

[EX Q]: Plankton has _ known ancestors.
[EX A]: two

[EX Q]: Rabbits have a life-span of about _ years, and require as much maintenance as a dog or cat.
[EX A]:
ten