3.A lot of contaminants, like lead or arsenic, won't be obvious without tests, but some clues, like cloudiness, brown or yellow coloration, a foul odor, or an excessive chlorine smell can indicate the need to investigate further.
许多污染物,如铅或砷,如果不进行测试就不会很明显,但一些线索,如混浊、棕色或黄色、恶臭或过多
氯
味,可能表明需要进一步调查。机翻