Naruto Episode 25
The last question is revealed to be a choice – stay and risk the chance of being disqualified forever from the exams, or leave and automatically fail. Many teams leave, but Naruto gives an inspiring monologue that gives the remaining teams the courage to stay. Ibiki reveals that the question itself was a test, and those who stayed automatically pass. The remaining Genin are left to the next instructor, Anko Mitarashi, who takes them all to the Forest of Death.
Source: Wikipedia
Naruto Episode 25 – The Tenth Question: All or Nothing
