Characteristics of Normal Curves Which of the following are characteristics of normal curves? Select one or more: Normal curves approach the horizontal axis, but never touch or cross it. O Normal curves are positively skewed, symmetric, or negatively skewed. Normal curves have an area of 1 between 3 standard deviations of the mean. Normal curves have an area under the curve of 1. Normal curves are symmetrical about a vertical line through the mean. Normal curves are bell-shaped with the highest point over the mean