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

[EX Q]: Bull sharks are a 'requiem' species, reaching up to _ feet in length.
[EX A]: ten

[EX Q]: Trees can also be air layered but air layering usually takes four to _ months to be successful.
[EX A]: six

[EX Q]: Humanity is responsible for _ or six billion tons a year.
[EX A]:
five