4 | | | | | 1. 1.7 | 2.5 | | 2. | | | | | | | | | | 3. | | | | | | | | | | | 4. | | | | 5. | 60% | | | 80% | | | 6. | 1. | 5 | 3mg/L | 1mg/L | 4 5 | | | |