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, Certificates contain 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 perhaps other 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.

74（）

A．communication

B．computation

C．expectation

D．expiration

你的公司出现了紧急状况，需要尽快做一些工作，这种情况下，把以下哪项加入合同最为有用（）

A、明确的工作说明

B、关于使用哪些分包商的要求

C、激励

D、不可抗力条款