肝性脑病产生机制有（）

A.血氨的储积

B.支链氨基酸／芳香氨基酸比例失调

C.假性神经递质学说

D.肠道呈酸性环境

E.肠道呈碱性环境

Traditional Internet access methods like dial-up were so slow that host computers were connected to the dial-up （71） at the customer premise over slow （72） ports.PPP was designed to run directly over these serial links. But with the advent of broadband Internet（73） technologies such as ADSL and cable modems there has been a considerable increase in the bandwidth delivered to the end users. This means that the host computers at the customer premise connect to the （74） or cable "modem" over a much faster medium such as Ethernet. It also means that multiple （75） can connect to the Internet through the sameconnection.

A．access

B． cache

C．cast

D．storage