Out of Aluminium, Copper, Calcium and Tin, the most reactive metal is _________?

The most reactive metal out of Aluminium, Copper, Calcium and Tin is Calcium.

Here's why:

Reactivity of metals is determined by how easily they lose electrons and form positive ions (cations). In the reactivity series, metals are arranged in order of their decreasing reactivity.

Calcium is a group 2 element and loses its outermost electrons more readily than Aluminium and Copper in group 13 and 14 respectively, and Tin in group 14. Therefore, Calcium is the most reactive metal among them.