The correct answer is B. 4MB.
Each pixel in a 24-bit color image is represented by 3 bytes, one for each of the red, green, and blue components. Therefore, a 1024×768 image requires 10247683 = 2,359,296 bytes of video RAM. Since 1MB is equal to 1,048,576 bytes, 2,359,296 bytes is equivalent to 2.27 MB. However, video RAM is typically rounded up to the nearest multiple of 8, so the amount of video RAM needed to display a 1024×768 image at 24-bit color is 4MB.
Option A is incorrect because 1MB is not enough video RAM to display a 1024×768 image at 24-bit color.
Option C is incorrect because 8MB is more video RAM than is needed to display a 1024×768 image at 24-bit color.
Option D is incorrect because 512KB is not enough video RAM to display a 1024×768 image at 24-bit color.
Option E is incorrect because 4MB is the correct answer.