英语中的破折号是代表对哪一部分的解释?外语高手请进~
例如：The sense organs that "connect" all animals to the outside world are merely transducers--instruments like a microphone,TV camera,or phonograph pickup arm--which convert one form of energy into another.
这两个破折号各指哪一部分的内容呢?有没有外语高手?