Final answer:
Curved lines arranged in opposite directions create a 'wave' pattern in art, representing a repeating visual motif resembling the motion of natural waves.
Step-by-step explanation:
The question asks about the visual effect created when curved lines are used in art. Curved lines, whether placed horizontally, vertically, or diagonally, are used to create a dynamic effect in artwork. Specifically, when these lines are repeated in opposite directions, they create a visual representation known as a wave.
Waves in art are characterized by their repetitive motion, similar to the undulating motion of water waves or the rhythmic pattern found in light waves. This visual motif can invoke a sense of movement and continuity, making it a powerful tool for artists to convey emotion or movement. The correct answer to the question is 'd. wave', as it refers to this repeating pattern that resembles the crests and troughs characteristic of waves in nature.