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.

the Hardware interface and a distribution （） called "Standard MIDI Files".

A．format

B．text

C．wave

D．center

对单一证券的风险的衡量就是对证券预期收益变动的可能性与变动幅度的衡量，只有当证券的收益出现负的变动时才能被称为风险。