Listen and fill
你将听到五组对话，根据对话内容填入所缺的单词, 使对话意思合理、完整，每空只填一词，注意大小写的规范要求，数字可以用阿拉伯数字表示。每组对话将读两遍。（每空1分，共5分)
（1）Teacher: How many traffic _______ are there in every country?
Student: There are always three: red, yellow and       .
（2）Amy: How do you            a tree ?
Chen: First, dig the          .
（3）My father is an            .