从下面提供的答案中选出应填入下列英文语句中______内的正确答案。 When most people refer to multimedia, they generally mean the combination of two or more continuous media, usually with some user (1) . In practice, the two media are normally audio and video, this is, (2) plus moving (3) . It should be obvious by now that transmitting multimedia material in uncompressed form is completely out of the (4) . The only hope is that massive compression is possible. Fortunately, a large body of research over the past few decades has led to many compression techniques and algorithms that make multimedia transmission (5) ．