51● 已经发布实施的现有标准（包括已确认或修改补充的标准），经过实施一定时期后，对其内容再次审查，以确保其有效性、先进性和适用性，其周期一般不超过__（65）__年。
A.1
B.3
C.5
D.7
开始考试练习点击查看答案52● MIDI enables people to use _（66）_ computers and electronic musical instruments.There are actually three components to MIDI, the communications " _（67）_ ", the HardwareInterface and a distribution _（68）_ called "Standard MIDI Files". In the context of the WWW, the most interesting component is the _（69）_ Format. In principle, MIDIfiles contain sequences of MIDI Protocol messages. However, when MIDI Protocol _（70）_ 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.
A.personal
B.electronic
C.multimedia
D.network
开始考试练习点击查看答案53● Certificates are _（71）_documents attesting to the _（72）_ of a public key to an individual or other entity. They allow verification of the claim that a given public key does in fact belong to a given individual. Certificates help prevent someone from using a phony key to _（73）_ someone else. In their simplest form, Certificatescontain a public key and a name. As commonly used, a certificate also contains an _（74）_date, the name of the CA that issued the certificate, a serial number, and perhapsother information. Most importantly, it contains the digital _（75）_ of the certificate issuer. The most widely accepted format for certificates is X.509 , thus, Certificates can be read or written by any application complying with X.509.
A.text
B.data
C.digital
D.structured
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