Which of the given properties belongs to non-metals? 

Brittle 

The correct answer is option 3. Brittle.

Brittle belongs to non-metals. The properties described are associated with the following:

Lustrous:  This property is characteristic of metals. Metals often have a shiny, reflective surface.

Ductile:  This property is also associated with metals. Ductility refers to the ability of a material to be stretched into a thin wire.

Malleable: This property is characteristic of metals. Malleability refers to the ability of a material to be hammered or rolled into thin sheets.

Brittle:  This property is typically associated with non-metals. Brittle materials tend to fracture or break when subjected to stress without significant deformation.