Answer:
D. Variations in color
Step-by-step explanation:
Bitmaps are images formed by pixels. But what would a Pixel be? A pixel is nothing more than a dot on your monitor, small and with varying colors and brightness. Suitable for representing images with a high level of detail. Bitmaps files, being formed by arranging the image pixel by pixel, if they have their size increased will suffer considerable distortions, and thus each point will be transformed into larger blocks to compose the larger image.
Bitmap illustrations can be, for example, nature photos. These images have a subtle tonal transition and are often composed of thousands of colors. The difficulty in working with bitmap graphics is that, when enlarging them, there will be a loss of definition and a great decrease in quality, so the enlargement of the images the pixels will be evident