State true or false.
Diamond and iodine are non-metals that are lustrous.

Basically, lustre is a quality that has to do with how minerals reflect light. Both metallic and non-metallic lustre have these two characteristics. Metals resemble flat pieces of steel or have a silvery sheen.  Translucent properties are present in non-metallic lustre.

In the periodic table, as we move down the group, the size of the iodine atom increases by lowering the shielding of the valency electron. by this the interaction between atoms and the outermost electron decreases.  The surface of iodine becomes excited by absorbing the heat energy from the light. and release the energy by emitting the light when they come into their normal, which appears their surface is lustrous. 
The cut, clarity, reflection, and refractive index of a diamond all contribute to its sparkling look. Diamonds found in nature are drab and dim. Partial shine is provided by total internal refraction. When light hits a diamond, it is refracted and split into different colours. Diamond is given a shine as a result.

Hence, the correct answer is option A.