Potassium (k) and copper (cu) are both in period 4. they both have
similar properties
the same number of protons
four electron shells
the same number of electrons

Option (c) is the correct answer.

Explanation:

It is known that period number of the periodic table helps in determining the number of shells present in the elements of the respective period.

For example, as potassium and copper both lie in period four which means that n = 4.

That is, the number of shells present in both potassium and copper is 4.

Whereas when elements are present in same group then they contain same number of valence electrons. Due to which elements of the same group tend to show similar chemical properties.

Therefore, we can conclude that potassium (K) and copper (Cu) are both in period 4. They both have four electron shells.