The correct answer is A. RAM.
RAM (Random Access Memory) is the fastest type of memory in a computer. It is used to store data that the computer is currently using. RAM is volatile, which means that it loses its contents when the computer is turned off.
ROM (Read-Only Memory) is a type of memory that stores data that cannot be changed. ROM is used to store the basic instructions that the computer needs to start up. ROM is non-volatile, which means that it retains its contents even when the computer is turned off.
CD-ROM (Compact Disc Read-Only Memory) is a type of optical disc that can store data. CD-ROMs are read-only, which means that the data on them cannot be changed. CD-ROMs are slower than RAM and ROM.
Hard disk is a type of storage device that stores data on magnetic disks. Hard disks are slower than RAM and ROM.
Therefore, the fastest data access time is provided by RAM.