Answer: A. color
A mineral can be defined as an inorganic compound that is obtained by digging up the earth crust. It is available in the ore deposits. The physical characteristics and chemical composition of the mineral can be used for the identification of the mineral.
Color, streak, luster and cleavage are physical characteristics of the mineral which can be useful for identification. Streak is a test in which the mineral is scratched to identify it's internal color for identification, luster means how a mineral shows reflection against the light, cleavage is the breaking of the mineral into parts, it tells the internal composition of the mineral.
Color is the least reliable method for identifying a mineral because two or more minerals can have the same color.