Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

[Q]: Erosion is divided into ____ main categories, water and wind.
[A]: two


[Q]: Airplanes still fly four to ____ times faster than zeppelins.
[A]: five


[Q]: Proprioceptive stimulation has ____ sources.
[A]:
two