Answer:
a. Line
Explantion
There are many different types of lines, all characterized by their length being greater than their width. Lines can be static or dynamic depending on how the artist chooses to use them. They help determine the motion, direction and energy in a work of art. We see line all around us in our daily lives; telephone wires, tree branches, jet contrails and winding roads are just a few examples.
Certainly the jagged, meandering lines of the lightning itself dominate the image, followed by the straight lines of the skyline structures and the coast line. There are more subtle lines too, like the lights along the buildings. Lines are even implied by the reflections in the water.