Answer:
a) Ionic
Explanation:
Natural and artificial compounds can be formed from two or more metals.
If the difference in electronegativity between the metals is very large, these compounds may be bonded by a mixture of chemical bonds. Those can be metallic bonds and other types of bonds.
According to the electronegativity difference between two components, if it is equal or higher than 1.7 they are classified as ionic bonding. In this sense, if we have two metals with a very large difference of electronegativity. Let's suppose higher than 1.7, they will form an ionic bonding.
Finally, Answer is a) Ionic bonding when the difference in electronegativity is very large.