input: OPTIONS:
- Energy layers
- Positive levels
- energy concentrations
- energy levels Now, answer this question: Q: Electrons are located at fixed distances from the nucleus, what are they called? A:
A:
output: energy levels

input: OPTIONS:
- fermentation
- excitation
- polarization
- depolarization Now, answer this question: Q: In neurons, what often involves gated sodium channels? A:
A:
output: depolarization

input: OPTIONS:
- three
- one
- six
- two Now, answer this question: Q: After fertilization, how many cells does a zygote form into? A:
A:
output:
two