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

[EX Q]: Sewage travels through _ different sets of pipes.
[EX A]: three

[EX Q]: Silkies have _ seasonal moults but little hair is dropped.
[EX A]: two

[EX Q]: Normal adults appear to require _ to eight hours of sleep per day on average.
[EX A]:
six