What causes surface discoloration on the skin?

Surface discoloration on the skin can arise from various factors, but the option that accurately captures the primary cause is the deposits of matter on the skin surface. This includes substances that can accumulate on the skin such as dirt, cosmetics, or other external materials, which may lead to a change in color or tone on the skin.

In the context of preparation for disposition, it's essential to consider how skin discoloration may be addressed. Understanding that surface discoloration can be due to external deposits helps in assessing the condition of the body and determining the best methods for cleaning and preparing the skin for viewing or burial.

To clarify the context of the other options: while decomposition processes in the body do lead to significant changes in color, they are typically more internal effects rather than surface discoloration. Absorption of chemicals used during embalming can also affect skin appearance, but these tend to involve changes beneath the surface more than visible surface discoloration. Lastly, natural bruising before death can indeed cause discoloration, but it is usually a specific phenomenon not related to external surface deposits.