电力线路纵联保护的信号主要有以下三种：1、（）；2、（）；3、（）。
参考答案：闭锁信号；允许信号；跳闸信号
Jenny was a little nervous in front of so many strangers at first. But when she glanced at Jack,
she immediately felt _____ . [ ]
A. in peace
B. in need
C. at a loss
D. at ease
如下程序显示的结果是______。 s=1 i=0 DO WHILE i＜8 s=s+i i=i+2 ENDDO s
