Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 31 to 35. History books recorded that...

* Hướng dẫn giải

Đáp án B 

câu trong bài “In the "sound-on-film" system, sound was recorded as a series of marks on celluloid which could be read by an optical sensor. These signals would be placed on the film alongside the image” -> như vậy: sound -> a series of marks -> placed on the film alongside the image” -> đáp án B