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

[Q]: Cubs emerge from the den when they are four to _ months old.
[A]: six


[Q]: Acrobats mount a single bicycle until _ people in all are stacked on top of it.
[A]: ten


[Q]: Many tortoises can retract their head, their _ limbs and tail into the shell for protection.
[A]:
four