题目

Many people learn English because it _______ widely _______ in the world. A. is; used                    B. was; used                 C. is; using                   D. was; using 答案：A5．如图表示一交流电的电流随时间而变化的图象，此交流电流的有效值是（　　）A．5$\sqrt{2}$AB．5AC．3.5$\sqrt{2}$AD．3.5A