如果采用两级8237A级联方式，最多可以构成 【9】 个DMA通道。

阅读下面的材料，然后根据材料内容回答问题。

     Annie lived alone in Chicago. One day, she fell down in her bedroom and broke her leg. So she tried to call her friend Lisa. But she dialed (拨打) a wrong number. The call reached Taylor, an 18-year-old girl.

She was a college student and she lived hundreds of miles away from Chicago.

     At that time Taylor was reading in bed. She thought it was somebody playing a joke. When she was

going to hang up the phone, she heard a woman saying “Help! Help! ” From it Taylor thought something

bad must have happened to the woman. After she got the woman’s name and address, Taylor called 911

at once. Then she tried to make Annie feel comfortable. She spoke to Annie on the phone till the doctors

arrived at Annie’s house. At last Annie was taken to hospital in time.

     As soon as Annie felt better, she wrote a letter to Taylor to thank her.

1. Who answered the telephone?  

2. How did Taylor help Annie?   

3. Why did Annie write the letter to Taylor?  

用万用表测量交流电压时，黑表笔应插入（）插孔。

A.“-”

B.“+”

C.“O”

D.任意

在利用s曲线比较建设工程实际进度与计划进度时，如果检查日期实际进展点落在计划s曲线的右侧，则该实际进展点与计划s曲线在纵坐标方向的距离表示该工程（）。

A.实际进度超前的时间

B.实际超额完成的任务量

C.实际进度拖后的时间

D.实际拖欠的任务量

鳄鱼皮有什么特点？

______可以连续向主机192.168.1.100发送测试数据包，直到按下Ctrl+C键中断。

A．ping 192.168.1.100-a

B．ping 192.168.1.100-n

C．ping 192.168.1.100-t

D．ping 192.168.1.100-w