cluster
The smallest unit of space on a hard drive that can be used to store a file is called a "sector." A sector typically holds 512 bytes of data, although newer hard drives may have larger sector sizes. Multiple sectors are grouped together to form clusters, which are used to store files on the hard drive.
Maybe you should check your book. <---- not very nice A Cluster
The smallest unit of space allocated to a file is a cluster or block, which is a contiguous group of sectors on a hard drive allocated to a single file. The size of a cluster can vary depending on the file system and the size of the disk.
drive space
As long as it shows up as some sort of icon or file, it may be put on the flash drive, but there must be space available in the flash drive.
Zipping compresses the file so that it takes up less space on the disk drive.
You should be able to save any file onto a USB flash drive provided the drive is working and there is adequate space on the drive for the file.
cluster
back up
A USB can store anything that can be represented by a computer file, so yes.
GIFs are small but poor quality.
a database file is a space to store thumbnails for a database