There was no s______ in movies before 1929 ,so people had to guess wha the actors were saying .
问题描述：
There was no s______ in movies before 1929 ,so people had to guess wha the actors were saying .
答
sound
常识题30年代的电影都是默片
题目后半段也说了：人们要猜演员在说什么
答
sound 1929年之前电影都是默片，没声音，观众只能猜测演员说什么了
（其实人家会插字幕的）
答
sound
1929年以前电影都没有声音,所以人们不得不猜测演员们在说什么.
答
填sound。整句意思是“1929年之前的电影都是无声的，所以那时的人们不得不猜测演员在说什么。”