Q: Given a passage and a question, find the answer to the question based on the passage. The answer should consist of only one word that lies in the span of only one of the sentences in the passage.
Paragraph: 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

A:
two