Answer:An element which is highly conductive, highly reactive, soft, and lustrous is most likely an alkali metal.
Explanation:Alkali metals are in group 1 of the Periodic table which means that they have only a single valence electron.
This causes them to be soft and highly reactive because:
The single valance electron leads to weak bonds amongst the element's atoms which makes them soft
The elements want to lose the single valance electron so as to become stable so they will react with other elements to give away the electron.
Examples of alkali electrons include:
Lithium
Sodium
Potassium etc
In conclusion therefore, alkali metals are highly reactive and soft and so the element described above is most likely an alkali metal.