instruction:
In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
question:
Healthy people can donate blood as often as once every _ weeks.
answer:
eight


question:
Rheas are brownish instead of black like the ostrich and have _ toes instead of two.
answer:
three


question:
Insects have _ lungs or centralized respiratory system.
answer:

no