Question

the highest-ranking nazi leader tried at nuremberg was
adolf hitler
alfred rosenberg
hermann goring
julius streicher

Explanation:

Adolf Hitler died by suicide before the Nuremberg Trials, so he was not tried. Alfred Rosenberg, Julius Streicher were mid-to-high ranking but not the highest among the tried defendants. Hermann Goring was Hitler's designated successor and the highest-ranking Nazi leader who was captured and put on trial at Nuremberg.

Answer:

Hermann Goring.