Modernist composers before world war i were mainly preoccupied with changing their approach to:

Modernist composers before World War I was mainly preoccupied with changing their approach to melody, harmony, and tonality. By means of Melody, they change it by having no longer top element. By means of harmony, they created no more functional harmony, the deliverance of dissonance and new measures. They also changed tonality approach to none tonal center. The tonal center was made in new techniques.

the answer is a. hope this