下列哪种方法是绝育措施（）
A.药物避孕
B.男用避孕套
C.体外排精
D.安全期避孕
E.双侧输精管结扎及粘堵术
参考答案：E
In the last few years thousands of films ________ all over the world.
A．have produced
B．have been produced
C．are producing
D．are being produced
无线网络优化的实质是什么？
