第28题: [单项选择]From the text we learn that Welchi ______. A. is a wicked worm causing as many damages as Blaster did B. is a program designed by Haley to detect worms like Blaster C. is a program intended to fix the infected machines D. is a worm meant to defeat the virus with "pings" 参考答案:C 答案解析:这是一道细节题。根据第五段内容可知,Welchi是一种修补电脑程序感染的软件,故答案为C。