Q: Context: The NSO is conducted on two levels each year. It was the first Olympiad to be conducted by SOF.It has been conducted since 1996. Students from class I-XII may participate in the examination.

Question: how many levels are there in science olympiad?
Let's give stream of consciousness below
The relevant information to answer the above question is: The NSO is conducted on two levels each year. So the answer is two levels.