Which situation is most likely an indicator that an economy has reached a trough?

It has previously hit a peak.

Explanation:

An econ omy is made of peaks and troughs, usually a peak indicates an incoming trough (i.e; roaring 20's became the Great Depression)

When the employment rate raises the economy most likely enter a contractionary phase. When the employment rate bottoms out, a trough has most likely occurred. Income and wages can also indicate where the economy stands.