SMA的主要优点有( )。

A．抗滑耐磨

B．空隙率小

C．抗疲劳

D．高温抗车辙

MIDI enables people to use （） computers and electronic musical instruments. There are actually three components to MIDI, the communications " （） ", the Hardware interface and a distribution （） called "Standard MIDI Files". In the context of the WWW, the most interesting component is the （） Format. In principle, MIDI files contain sequences of MIDI Protocol messages. However, when MIDI Protocol （） are stored in MIDI files, the events are also time-stamped for playback in the proper sequence. Music delivered by MIDI files is the most common use of MIDI today.

In the context of the WWW, the most interesting component is the （） Format.

A．Video

B．Faxmail

C．Graphic

D．Audio