What is a good indicator of water quality? 

A)  the number of coliform bacteria in the water body 
B)  the number of ducks in the water body 
C)  the number of fish in the water body 
D)  the number of snakes in the water body

The number of coliform bacteria in the water is a good indicator of water quality because coliform bacteria are an indicator species that can demonstrate the presence of other types of harmful bacteria, viruses, and parasites that can be harmful to human health if consumed. High levels of coliform bacteria in drinking water, for example, can be an indication of possible sewage contamination, agricultural runoff, or other sources of pollution.