What is a key identifying feature of the German cockroach?

The key identifying feature of the German cockroach is the single light stripe on their back, which is particularly noticeable in the nymph stage. This distinct marking runs from the head to the wings and is a reliable visual cue for identification. German cockroaches are typically brown, and while they do possess long antennae and dark bodies as adults, these characteristics are not unique to them and can be observed in other cockroach species as well.

Other options provided might describe features that could apply to various cockroach species but lack the specificity that the light stripe provides for identifying German cockroaches accurately. The bright red coloration, for instance, is not characteristic of German cockroaches, making it easy to eliminate as a key identifier.