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

Ex Input:
Plasma levels fall by about a half within three to _ hours.

Ex Output:
four

Ex Input:
Spatial sensors work in one, two, or _ dimensions.

Ex Output:
three

Ex Input:
Enzymes often catalyze reactions with two substrates and _ products.

Ex Output:
two