Answer: Option (2) is the correct answer.
Step-by-step explanation:
In solid state, substances or elements that contain unpaired electrons are able to conduct heat and electricity.
This is because for conducting heat and electricity availability of free or unpaired electrons is necessary.
For example, atomic number of copper is 29 and its electronic distribution is 2, 8, 18, 1.
Whereas ionic compounds can only conduct heat and electricity when they are present in aqueous solution.
This is because then they are dissociated into ions.
Thus, we can conclude that Cu is the solid which most easily conduct electricity.