Among K, Ca, Fe and Zn, the element which can form more than one binary compound with chlorine is

A binary compound is one made of two different elements.These can be one of each element such as CuCl or FeO These can also be several of each element such as Fe2O3  or   SnBr4.Metals which have variable oxidation number can form more than one type of binary compounds like Fe shows the oxidation state +2 and +3. Hence it forms two types of binary compounds, e.g., FeCl2,  FeCl3.