练习材料：
NCE--第四册
Lesson 38-3 Water and the traveler
Alcohol may be a medical disinfectant, but should not be relied upon to sterilize water. Ethanol is more effective at a concentration of 50-70 per cent; below 20 per cent, its bactericidal action is negligible. Spirits labelled 95 proof contain only about 47 per cent alcohol. Beware of methylated alcohol, which is very poisonous, and should never be added to drinking water. If no other safe water supply can be obtained, tap water that is too hot to touch can be left to cool and is generally safe to drink. Those planning a trip to remote areas, or intending to live in countries where drinking water is not readily available, should know about the various possible methods for making water safe.
[ˈælkəhɒl] [meɪ] [biː] [ə] [ˈmɛdɪkəl] [ˌdɪsɪnˈfɛktənt], [bʌt] [ʃʊd] [nɒt] [biː] [rɪˈlaɪd] [əˈpɒn] [tuː] [ˈstɛrɪlaɪz] [ˈwɔːtə]. [ˈɛθənɒl] [ɪz] [mɔːr] [ɪˈfɛktɪv] [æt] [ə] [ˌkɒnsənˈtreɪʃən] [ɒv] 50-70 [pɜː] [sɛnt]; [bɪˈləʊ] 20 [pɜː] [sɛnt], [ɪts] bactericidal [ˈækʃ(ə)n] [ɪz] [ˈnɛglɪʤəbl]. [ˈspɪrɪts] [ˈleɪbld] 95 [pruːf] [kənˈteɪn] [ˈəʊnli] [əˈbaʊt] 47 [pɜː] [sɛnt] [ˈælkəhɒl]. [bɪˈweər] [ɒv] methylated [ˈælkəhɒl], [wɪʧ] [ɪz] [ˈvɛri] [ˈpɔɪznəs], [ænd] [ʃʊd] [ˈnɛvə] [biː] [ˈædɪd] [tuː] [ˈdrɪŋkɪŋ] [ˈwɔːtə]. [ɪf] [nəʊ] [ˈʌðə] [seɪf] [ˈwɔːtə] [səˈplaɪ] [kæn] [biː] [əbˈteɪnd], [tæp] [ˈwɔːtə] [ðæt] [ɪz] [tuː] [hɒt] [tuː] [tʌʧ] [kæn] [biː] [lɛft] [tuː] [kuːl] [ænd] [ɪz] [ˈʤɛnərəli] [seɪf] [tuː] [drɪŋk]. [ðəʊz] [ˈplænɪŋ] [ə] [trɪp] [tuː] [rɪˈməʊt] [ˈeərɪəz], [ɔːr] [ɪnˈtɛndɪŋ] [tuː] [lɪv] [ɪn] [ˈkʌntriz] [weə] [ˈdrɪŋkɪŋ] [ˈwɔːtər] [ɪz] [nɒt] [ˈrɛdɪli] [əˈveɪləbl], [ʃʊd] [nəʊ] [əˈbaʊt] [ðə] [ˈveərɪəs] [ˈpɒsəbl] [ˈmɛθədz] [fɔː] [ˈmeɪkɪŋ] [ˈwɔːtə] [seɪf].
任务配置：
L0+L4
知识笔记 ：
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