题目

After the Arab states won independence, great emphasis was laid on expanding education, with girls as well as boys _____ to go to school. A. to be encouraged                    B. been encouraged C. encouraged                     D. be encouraged 答案：C1、温室效应对人类的危害日趋严重．现己证实引起温室效应的主要气体是（　　）A、O2B、N2C、SO2D、CO2