Which of the following alkali metals has highest specific heat?

Lithium has the highest specific heat capacity of any solid element. Because of its specific heat capacity, the highest of all solids, lithium metal is often used in coolants for heat transfer applications. It belongs to the alkali metal group of chemical elements. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable. For this reason, it is typically stored in mineral oil.