The work is structured harmonically into a 12-bar blues pattern, and features a succession of solos for individual instruments, ending with the full ensemble. What characteristics do the beginnings of each instrumental solo have in common

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.