在主机遥控系统中，电动执行机构中的交流伺服系统得到越来越多采用是得益于（）的发展。

性质相同且近似服从正态分布的实验数据所求得的算术平均数标准差和标准误分别为和S，则区间［-1.96s，+1.96s］所代表的含义为（） |条件同上，问区间［-1.96，+1.96］所代表的含义为（）

A.它是总体均数的95%置信区间

B.它是总体均数（μ）的5%置信区间

C.它是该指标的95%正常值范围

D.它是该指标的99%正常值范围

E.它是该指标的99%可信区间

在窗体中添加一个命令按钮和一个文本框，并编写如下程序代码：
Private Sub Command1_Click()
k=0
Do While k ＜ 70
k=k+2
k=k*k+k
a=a+k
Loop
Text1．Text=a
End Sub
程序运行后，文本框中显示的是

A．20

B．32

C．44

D．78

( )用于检测引发心理行为问题的社会性因素。

A．社会适应量表
B．人格测验
C．生活质量量表
D．SCL—90

简述公钥证书使用有效性条件

Electronic mail, or mail, as it is known to its many fans, has been around for over two decades. Typically, email systems support five basic functions, as described below. (41) refers to the process of creating messages and answers. (42) refers to moving messages from the originator to the recipient. (43) has to do with telling the originator what happened to the message. Was it rejected Was it lost (44) incoming message is needed. So people can read their email. (45) is the final step and concerns what the recipient does with the message after receiving it.

A．Composition

B．Transfer

C．Reporting

D．Displaying