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Three functions $f_{1}(t), f_{2}(t)$ and $f_{3}(t)$, which are zero outside the interval $[0, T]$, are shown in the figure. Which of the following statements is correct?

1. $f_{1}(t)$ and $f_{2}(t)$ are orthogonal
2. $f_{1}(t)$ and $f_{3}(t)$ are orthogonal
3. $f_{2}(t)$ and $f_{3}(t)$ are orthogonal
4. $f_{1}(t)$ and $f_{2}(t)$ are orthonormal