SCSI interfaces provide for faster data transmission rates (up to 80 megabytes per second) than standard serial and parallel ports. In addition, you can attach many devices to a single SCSI port, so that SCSI is really an I/O bus rather than simply an interface Which two statements about SCSI are true?（）

• A、The bus is limited to 64 devices.
• B、It is a full-duplex serial standard.
• C、It is a half-duplex serial standard.
• D、It allows up to 320 MB/s of shared channel bandwidth.