MCQOPTIONS
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| 1. |
For surface water system, the required residual disinfectant concentration may not be less than _______ mg/L for more than ___________ hours before the first customer. |
| A. | 0.2, 6 |
| B. | 2.0, 6 |
| C. | 0.2, 4 |
| D. | 2.0, 4 |
| Answer» D. 2.0, 4 | |