Answer:
a. 4s
Explanation:
The outer energy level and sublevel used in the electron configuration for potassium is the 4s sub-level.
Potassium has 19 electrons.
The electronic configuration of this chemical element is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
The outermost energy level is the 4s
