What musical element occurs when a rhythm of four is played over a rhythm of three?

polyrhythm

Explanation:

In music, the concept of Polyrhythm presents itself as the simultaneity of two conflicting rhythms. Stylization of the cantochon, by means of the repetition of notes, of the abundant use of quateralters of varied number of elements and of polyrhythmia. Polyrhythmia can serve as a bridge to group improvisation in music.

i would say the answer is b. zigzag lines of the leaves. i believe this is the answer because zigzag lines go in different direction while the other options like: the vertical lines of the trees, the dotted lines on the road, and the curved lines of the park benches go in one direction.