What is meant by "the energy of an electron is quantized"? The quantity of electron energy can be measured.
Each electron around an atom has a discrete amount of energy.
The quantity of electron energy changes as it moves around the nucleus.
all of the above

d: All of the above. Have a nice day!

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.