Answer:
2. a region about the nucleus in which an electron of specified energy will probably be found
Explanation:
With quantum mechanics we can find the wave function that describes the movement of the particles, the interpretation of this wave function is through the probability density (φ* φ).
This probabilistic interpretation of the energies, position and amounts of motion electrons allow us to find the region around the nucleus where an electron of specific energy can be found with a given probability.
The correct answer is 2