The notes are changing in the following way:
- E to D-sharp: This is a half step down.
- F to F-sharp: This is a half step up.
- G to A-flat: This is a half step up.
Thus, the overall changes consist of a mixture of half steps up and down. Therefore, the correct response is "by a mixture of whole and half steps." However, since there is not a whole step in this situation (only half-step changes), a more accurate description is "by a mixture of half steps." If we had to choose from the given options, the best fit is “by a mixture of whole and half steps” due to the half-step nature but includes one whole-step classification for F to F-sharp which could sometimes be likewise misinterpreted as a whole-step change. All in all, half-steps primarily dictate the change, defining key transitions as well.
So based on that, the final response could lean towards "by a mixture of whole and half steps" due to the combination nature overall in different segments but mainly reflecting strict half notes.