Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[EX Q]: Pressure and vibration are examples of physical type of stimuli.
[EX A]: Pressure and vibration are examples of what type of stimuli?

[EX Q]: Collision frequency is greater for homogeneous category of catalysts, which also tend to be more sensitive to temperature and more 'expensive'.
[EX A]: Collision frequency is greater for what category of catalysts, which also tend to be more sensitive to temperature and more 'expensive'?

[EX Q]: Because action potentials are so brief, a neuron can produce hundreds per second.
[EX A]:
Because action potentials are so brief, a neuron can produce hundreds per what?