What characteristic is unique to the Mixolydian mode among the listed modes?

The unique characteristic of the Mixolydian mode lies in its particular arrangement of whole and half steps, especially in relation to half steps occurring between the notes. In the case of Mixolydian, the sequence of whole and half steps is primarily defined by the presence of a flat seventh degree, which distinguishes it from the major scale.

In Mixolydian, there is a half step between the fifth and sixth degrees. This step is critical because it contributes to the distinct sound of the mode, giving it a more bluesy or folky feel compared to the major scale, which has a whole step in this position. By identifying half steps between the first and second notes, as well as the fifth and sixth, we recognize this unique construction.

The other options describe half step intervals that do not accurately represent the characteristic structure of the Mixolydian mode. Most commonly, the Mixolydian mode is compared to the traditional major scale, leading to confusion with other modes. However, the placement of half steps within the Mixolydian mode remains uniquely identifiable, particularly between the fifth and sixth degrees, highlighting its distinctive tonal quality.