题目

--The prison was ___________ fire last night. --Someone must have set fire___________ it. A. on ; with     B. on ; to     C. over; with    D. should 答案：B下列关于方程的两个根的说法中正确的是 [　　] A．符号相同B．符号相反 C．有一根为0D．符号无法确定