Answer:
Mg and Zn
Explanation:
In cathodic protection, the sacrificial anode corrodes instead of the cathode which it protects. The anode is usually higher than the cathode in the electrochemical series. This also means that the reduction potential of the sacrificial anode is more negative than that of the cathode. Consider the reduction potentials of the metals listed in the question:
Mg=-1.185V
Zn= -0.7618V
Ag= +0.7996V
Au= +1.629V
Ni= -0.251V
The reduction potential of the cathode stated in the question is -0.447V hence only magnesium and zinc can function as sacrificial anode.