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 (66) ciphers, information is encrypted with (67) both the sender and receiver hold privately. Public - key encryption methods are called (68) ciphers, (69) created for each user, encryption key and decryption key ale (70) .

A．synchronous

B．Asynchronous

C．symmetric

D．asymmetric

下列关于丰胸按摩注意事项的说法，哪项是错误的（）。

A、做丰胸按摩时手法以刺激 * * 促进其血液循环为主

B、做健丰按摩时手法以 * * 上方胸大肌为主

C、大 * * 力度宜重，小 * * 力度宜轻

D、向双乳内、上方按摩时用力要实，要到位