下列选中关于IPv6的任播地址，所有说法中正确的是（）A、IPv6的任播地址用于取代

A mortgage-backed security has the following characteristics: It was created by pooling a collection of more than a thousand mortgages Not all investors face the same prepayment risk Investors receive three distinct kinds of cash flows Freddie Mac issued the security This security is a(n):（）

A. collateralized mortgage obligation.

B. stripped mortgage-security.

C. mortgage passthrough security.

决定血浆pH值的主要缓冲对是

A．KHCO3／H2CO3

B．K2HPO4／KH2PO4

C．NaHCO3／H2C03

D．Na2HPO4／NaH2PO4

E．蛋白质-Na／蛋白质

关于肾积水，下列不正确的是（）。

A.任何情况下，肾窦部出现宽10mm以上无回声区均可诊断为轻度肾积水

B.肾实质不同程度萎缩为重度肾积水的特征

C.中度肾积水肾外形无明显改变

D.声像图上肾窦回声分离不能一概认为是肾积水

E.重度肾积水时多个囊腔连通

电气变电所的运行岗位应做的分析主要内容是什么？