1. A liquid crystal display, comprising: a plurality of dots arranged in a matrix formed with pixel columns and pixel rows, wherein each of the dots comprises at least a pixel and is used for displaying a dot of a first resolution image, and the dot size is equal to or larger than 0.018 mm 2 and equal to or smaller than 0.16 mm 2 , wherein when the liquid crystal display receives a second resolution image signal having dots fewer than the first resolution image, a dot of a second resolution image is displayed by at least a high gray level pixel and at least a low gray level pixel which displays a gray level lower than the high gray level pixel, and each of the pixel rows is formed by a plurality of the high gray level pixels or a plurality of the low gray level pixels, and wherein when the liquid crystal display receives the first resolution image signal, each of the pixel columns is supplied with driving signals having the same polarity, and when the liquid crystal display receives the second resolution image signal, each of the pixel columns is supplied with driving signals having the same polarity.