It's not easy to let young people accept the ways of the old. It's becoming e____ more difficult in the face of new technologies. So officers gathered in Wuhan, Hubei Province that is proved to be good at m____ children interested in tradition. They shared some lessons. As we all know, many students know little about traditional things. Officers d____ how to make local operas popular in elementary and middle schools. Officers also agreed that every student should get the chance to w____ a traditional opera show for free every year.

    The work of the theatre was divided into three p____: speech, teaching and performance. By the end of November, about 146 e____ of these kinds were held. Opera artists are often invited to schools to communicate with students and teachers. Traditional opera lessons are t____ in more than 80 percent of its elementary and middle schools. More than 6,600 opera shows were performed at schools that year, and that was h____ praised by students and parents.

    In this way students can have a taste of the traditional beauty of China. "At first I was afraid these events could be a distract (分心) from study. Now I r____ that our children have learned a lot from them," said one parent of No.71 Middle School. One of the officers said o____ parts of the country could learn some lessons from Hubei Province's experiences. They hope students all over China will have the chance to learn the art of traditional operas by the end of 2018.

一本数学书长21米．

如图，直线 与 轴交于点 ，则 时， 的取值范围是____。

用反证法证明“两直线平行，同位角相等”时，可假设​ ____