instruction:
Given a scientific question, generate a correct answer to it.
question:
What are the ice crystals that form on the ground called?
answer:
frost

question:
What is the place called where the axon of one neuron meets the dendrite of another?
answer:
synapse

question:
Controlled variables are kept what to prevent them from influencing the effects of the independent variable on the dependent variable?
answer:
constant