From all the options available, the best answer to the blank space given would be (A) byte.
Although nanobyte might seem to be the answer, it actually does not exist as a unit of storage. The smallest unit of storage would actually be bit – bit is valued at either 1 or 0. A byte contains roughly 8 bits. One megabyte is approximately 1,024 kilobytes or 1,048,576 bytes – while one gigabyte is roughly 1,024 megabytes, which in bytes are around 1,073,741,824.