The correct option is C.
Silica, also called quartz is a natural mineral which is used for a lot of purposes. The normal activities that are carried out on silica such as cutting, grinding and drilling produce silica dusts. The silica dusts are very tiny and can easily be breathed into the lungs. Breathing in of silica dusts usually results in lung diseases such as lung cancer.
When working around silica dust, it is best to clean up as often as possible.