Final answer:
Disks are convenient for secondary storage due to random access and direct access capabilities.
Step-by-step explanation:
The characteristics of disks that make them convenient for secondary storage include the ability to read a block from the disk, modify it, and write it back into the same place. This is known as random access, which allows for efficient data manipulation. Disks can also access any block of information directly, meaning they can quickly locate and retrieve specific data.