Between these word choices, I would say tracks...as in traces/tracks one's steps...The other's don't really match the meaning of the word "traces"...hope this helps!
In the context of searching or investigation the word traces is similar find, discover, detect, find, uncover.
The alternatives that are shown in the screen, chains, harness, evidence and tracks i would like to comment their meanings so close to traces.
Chains: a sequence of items of the same type forming a line.
Screen: Something that shelters, protects or hides.
Evidence: Information indicating whether a belief or proposition is true or valid.
Harness: Control and make use of natural resource especially to produce energy.
According these definition the best synonym of traces is evidence.
