A warning signal suddenly appeared on the screen of my puter, the puter was being attacked by a certain virus.
A. indicated
B. indicating
C. to indicate
D. having indicated
网友回答
A. indicated
(答案→)B. indicating
C. to indicate
D. having indicated
解析：考查非谓语动词。signal和indicate是主谓关系，应该用现在分词表示伴随状况。句意：一个提示信号突然出现在我的电脑屏幕上，暗示电脑被病毒袭击了。故选B。