A:一定是直线
B:一定是曲线
C:可能是直线,也可能是曲线
D:可能是圆
①具有文化传递和共享的功能
②是对外文化交流的重要手段
③选择、创新的功能
④为文化传播提供了正确的方向保证
He fell off the bike and hurt his leg yesterday._______, he had to stay at home for two or three months.