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 deception key are (75)

A．synchronous

B．Asynchronous

C．symmetric

D．asymmetric

描述集合小管的错误项是( )。

A．弓形集合小管与远端小管曲部相连

B．弓形集合小管分布于皮质迷路

C．小管上皮细胞着色深，细胞界限不清

D．上皮细胞具有分泌H⁺、HCO₃的功能

E．是尿液浓缩的重要场所