Read this and answer the question. If the question is unanswerable, say "unanswerable".

Opponents argue that the death penalty is not an effective means of deterring crime, risks the execution of the innocent, is unnecessarily barbaric in nature, cheapens human life, and puts a government on the same base moral level as those criminals involved in murder. Furthermore, some opponents argue that the arbitrariness with which it is administered and the systemic influence of racial, socio-economic, geographic, and gender bias on determinations of desert make the current practice of capital punishment immoral and illegitimate.

What do death penalty opponents argue that capital punishment is effective at doing?
unanswerable