One instrument playing is normally indicated by the word - Sola - tutti - solo - soli

Solo

Explanation:

Solo is from a  Latin word that is solus and it means alone

true

that is the way that they talked back then

=)

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.