Q. In ggplot2, how do you add a color gradient to a scatter plot based on a numeric variable color_var?

• (A) scale_fill_gradient(low = "blue", high = "red")
• (B) color_gradient(low = "blue", high = "red")
• (C) scale_color_gradient(low = "blue", high = "red")
• (D) geom_point(aes(color = color_var), fill = "blue")