The correct answer is C. The goals of art are constantly changing. The concept of art is subjective, meaning that there's not one sole authority who says what art as a whole is trying to achieve. Instead, the goal of art will change depending on who's making and/or viewing it. Option A is incorrect because realistic painting is confined to a specific movement and time period, meaning that it wasn't always an important goal of art. Option B is incorrect, because an artist will often explain the goal of their work. Option D is incorrect, because artists are often influenced by previous movements, by muses, by education, etc.