Question

most substances that are not metals look dull. why? they are not ductile. they lack luster. they are not malleable.

Explanation:

To determine why non - metals look dull, we analyze each option:

• Option "They are not ductile": Ductility refers to the ability to be drawn into wires. This property has no direct relation to the appearance of being dull or shiny. So this option is incorrect.
• Option "They lack luster": Luster is the property of a substance to shine or have a shiny appearance. Non - metals generally do not have this property of luster, which is why they look dull. This option correctly explains the dull appearance of non - metals.
• Option "They are not malleable": Malleability is the ability to be hammered into thin sheets. This property is not related to the visual appearance of being dull. So this option is incorrect.

Answer:

B. They lack luster.