阅读理解

B

       When people go to the movies today, they can watch and listen to a story. But when the movie first appeared (出现) many years ago, there was no sound or music. Those silent (无声的) movies play an important role in movie history.

         When movie theatres showed silent movies, musicians were often there to play music along with the movie. Sometimes, musicians also made some special sounds. However, there was no sound in the movie itself. People learnt the story through the actors, the musicians and words on the screen. When movies first had sound, not everyone liked it. Many silent movie actors thought it was hard to act in the new kind of movies. Clara Bow was a famous silent-movie actress in the early 1920s. She was so nervous (紧张的) about her voice  that she couldn't become a star in the world of talking pictures. She then left show business (演艺界).

          The Jazz Singer (1927) was the first movie with sound. Talking pictures became a big success, and there were more and more movies like that. Later, silent movies became history.

根据材料内容选择最佳答案。

小明的解题思路是：如图2，过P作PE∥AB，通过平行线性质，可得∠APC=50°+60°=110°．

问题迁移：

简要说明细胞分裂对生物体的重要意义。

从方框中选择恰当的短语，并用其适当形式填空。