ANSWER
Option 3
EXPLANATION
Two notes are said to be an octave apart when the frequency of one note is exactly 2 times the other. In other words, it has twice as many waves.
Let us calculate the ratio of each option:
[tex]\begin{gathered} \Rightarrow\frac{512}{256}=2 \\ \Rightarrow\frac{524}{262}=2 \\ \Rightarrow\frac{622}{331}=1.88 \\ \Rightarrow\frac{554}{277}=2 \end{gathered}[/tex]As we can see, only in option 3 is the higher frequency not exactly 2 times the lower frequency.
Therefore, the answer is option 3.
