What type of impression is classified as a plastic fingerprint?

A plastic fingerprint is defined as a three-dimensional impression of a fingerprint that is created when a finger leaves an indented mark in a soft material. The option specifying an imprint made in wax or soap correctly represents this definition, as both wax and soap have properties that allow for such detailed impressions to occur. These materials can capture the ridge details of the fingerprint, making them valuable in forensic investigations.

In contrast, other materials mentioned do not create true three-dimensional impressions. While blood can leave a mark, it creates a two-dimensional transfer rather than a plastic impression. Dust can leave prints, but they are typically more akin to latent prints, which are often two-dimensional. Imprints made on paper also do not qualify as plastic, as they are generally flat prints, lacking the depth necessary to be classified in this way. Thus, the classification of an impression made in wax or soap as a plastic fingerprint is clearly accurate in the context of forensic science.