Describe some methods used to clean polluted water, including the use of biotechnology

Bacteria have a well-earned reputation for causing disease, but now certain types of microorganisms are being put to good use by improving water cleanliness and safety.  Waste water produced by factories is contaminated with heavy metals—elements that are naturally present in our bodies in small amounts, but which can be extremely dangerous to humans at higher levels of concentration.  To clean this industrial waste water, it is put through the process of bioremediation, or the use of microorganisms to treat water that has been contaminated by hazardous materials. Water that has been cleaned by this method can then be released into the environment or even reused. One method of bioremediation is called biogenic hydrogen sulfide precipitation technology

The answer is  a.first and third quarters