练习材料：
NCE--第四册
Lesson 20-1 Snake poison
How it came about that snakes manufactured poison is a mystery. Over the periods their saliva, a mild, digestive juice like our own, was converted into a poison that defies analysis even today. It was not forced upon them by the survival competition; they could have caught and lived on prey without using poison, just as the thousands of non-poisonous snakes still do. Poison to a snake is merely a luxury; it enables it to get its food with very little effort, no more effort than one bite. And why only snakes? Cats, for instance, would be greatly helped; no running fights with large, fierce rats or tussles with grown rabbits -- just a bite and no more effort needed.
[haʊ] [ɪt] [keɪm] [əˈbaʊt] [ðæt] [sneɪks] [ˌmænjʊˈfækʧəd] [ˈpɔɪzn] [ɪz] [ə] [ˈmɪstəri]. [ˈəʊvə] [ðə] [ˈpɪərɪədz] [ðeə] [səˈlaɪvə], [ə] [maɪld], [dɪˈʤɛstɪv] [ʤuːs] [laɪk] [ˈaʊər] [əʊn], [wɒz] [kənˈvɜːtɪd] [ˈɪntuː] [ə] [ˈpɔɪzn] [ðæt] [dɪˈfaɪz] [əˈnæləsɪs] [ˈiːvən] [təˈdeɪ]. [ɪt] [wɒz] [nɒt] [fɔːst] [əˈpɒn] [ðɛm] [baɪ] [ðə] [səˈvaɪvəl] [ˌkɒmpɪˈtɪʃən]; [ðeɪ] [kʊd] [hæv] [kɔːt] [ænd] [lɪvd] [ɒn] [preɪ] [wɪˈðaʊt] [ˈjuːzɪŋ] [ˈpɔɪzn], [ʤʌst] [æz] [ðə] [ˈθaʊzəndz] [ɒv] [nɒn]-[ˈpɔɪznəs] [sneɪks] [stɪl] [duː]. [ˈpɔɪzn] [tuː] [ə] [sneɪk] [ɪz] [ˈmɪəli] [ə] [ˈlʌkʃəri]; [ɪt] [ɪˈneɪblz] [ɪt] [tuː] [gɛt] [ɪts] [fuːd] [wɪð] [ˈvɛri] [ˈlɪtl] [ˈɛfət], [nəʊ] [mɔːr] [ˈɛfət] [ðæn] [wʌn] [baɪt]. [ænd] [waɪ] [ˈəʊnli] [sneɪks]? [kæts], [fɔːr] [ˈɪnstəns], [wʊd] [biː] [ˈgreɪtli] [hɛlpt]; [nəʊ] [ˈrʌnɪŋ] [faɪts] [wɪð] [lɑːʤ], [fɪəs] [ræts] [ɔː] [ˈtʌslz] [wɪð] [grəʊn] [ˈræbɪts] -- [ʤʌst] [ə] [baɪt] [ænd] [nəʊ] [mɔːr] [ˈɛfət] [ˈniːdɪd].
任务配置：
L0+L4
知识笔记 ：
练习感悟：
今天是课文第二部分，要注意单词重音以及词性。单词mild[maɪld]中的i，发[aɪ]的音，以往发音错了，纠正。
