Since there are 1024 bytes in one kilobyte, to convert bytes to kilobytes, you divide the number of bytes by 1024. Therefore, for an image file size of 4000 bytes, dividing by 1024 gives you approximately 3.90625 kilobytes. However, it's common to round to the nearest whole number in everyday usage, so the closest correct answer is 4 KB, which is a slight overestimation. A choice of exactly 3.90625 KB is not provided, as it is standard practice to round to the nearest kilobyte. An answer of 3 KB would be an underestimation, and 1 KB and 2 KB are significantly lower than the actual size.