Kr look on periodic table it's krypton elements
Answer:
a new discover a new theory
The fourth combination is not allowed.
The third quantum number, i.e. m subscript l, only may an integer number from -l to + l. Given that l = 0, the only allowed m subscript l is 0.
I believe it is A because a physical change is something that can be changed back to where a chemical change can not be such as burning something.