题目：
多选题
Listening is the most difficult skill because＿＿＿.
- A. the listener cannot control the content or speed.
- B. a listener cannnot look back at what he has heard.
- C. Speech may contain redundancy, hesitation, sudden changes of topic and so on.
- D. the listener sometimes fails to recognize the signals or discourse markers in speech.
答案：
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