在我国并不是所有的工程在开工前都需要办理施工许可证，下列( )等工程不需要办理。

A．作为文物保护的建筑工程

B．军用房屋建筑

C．临时性建筑

D．抢险救灾工程

E．工程投资额在50万元以下的建筑工程

In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet. There are two types of key technology: private key and public key. Private-key encryption methods are called (71) ciphers, information is encrypted with (72) both the sender and receiver hold privately. Public-key encryption methods are called (73) ciphers, (74) created for each user, encryption key and decryption key are (75)

A．synchronous

B．Asynchronous

C．symmetric

D．asymmetric