Which adapter connects two or more integrated hard disks?

The RAID adapter is specifically designed to connect two or more integrated hard disks and manage them as a single logical unit. It provides functionality such as redundancy, performance improvement, and storage pooling, depending on the RAID level implemented. This enables features like data striping, mirroring, or parity, which enhance data integrity and provide faster access speeds across multiple drives.

The other options serve different functions: a USB adapter is primarily used for connecting USB devices, a modem adapter facilitates internet connectivity through telecommunication systems, and a wireless NIC (Network Interface Card) is used to connect a device to a wireless network. None of these options offer the specific capabilities or functions necessary for managing and connecting integrated hard disks in a RAID configuration like a RAID adapter does.