对于不擅长编程的初中级用户，在进行选用多媒体制作时可以选用操作简单，易于上手的（）。

关于总监理工程师负责制原则所体现的权责主体的说法，正确的是（　　）。

A．总监理工程师既是工程监理的责任主体，又是工程监理的权力主体

B．总监理工程师只是工程监理的责任主体，不是工程监理的权力主体

C．总监理工程师既是工程监理的权利主体，又是工程监理的责任主体

D．总监理工程师只是工程监理的权利主体，不是工程监理的责任主体

三相负载星形联接时，线电流必等于相电流

An analog signal’s characteristic quantity representing data may 66) . at any instant, any value within a continuous (67) . For example, an analog signal may follow continuously the values of another physical quantity representing data.

A discrete signal is composed of (68) elements in time, each element having one or more characteristic quantities which can represent data. Examples of characteristic quantities are amplitude, waveform, (69) , and position in time. A digital signal is a special case of discrete signals, in which data are represented by a (70) number of well-defined discrete values that one of its characteristic quantities may take in time.

（69）处填（）。

A．duration

B．period

C．persistence

D．span

井控是油气井（）的简称。

试管棉塞的旋进的长度应为棉塞长度的（）。

A.1/3

B.1/4

C.2/3

D.1/5