The correct answer is option-3, City of gold. Multan was named by the Arabs as the City of gold. This name refers to the richness and prosperity of the city, particularly in terms of trade and commerce. Multan has a long history of being a significant trading hub in the region, attracting merchants from various parts of the world. The Arabs, who were involved in extensive trade with Multan, recognized its economic importance and hence named it the City of gold. This name symbolizes the city`s wealth and prosperity during ancient times. It is important to note that Multan is also known for its historical and cultural significance, but the Arabs specifically referred to its prosperity as represented by the name City of gold.